are pure metals made of atoms or ions
atoms
face-centered cubic (fcc), and hexagonal close-packed (hcp). In bcc, each atom is positioned at the center of a cube of eight others. In fcc and hcp, each atom is surrounded by twelve others, but the stacking of the layers differs. Some metals adopt different structures depending on the temperature. The unit cell for each crystal structure is the smallest group of atoms which has the overall symmetry of the crystal, and from which the entire crystalline lattice can be built up by repetition in three dimensions. In the case of the body-centered cubic crystal structure shown above, the unit cell
Metal
This definition often breaks down since many substances in ordinary experience, such as rocks, salts, and metals, are composed of large crystalline networks of chemically bonded atoms or ions, but are not made of discrete molecules. Molecules are held together by either covalent bonding or ionic bonding. Several types of non-metal elements exist only as molecules in the environment. For example, hydrogen only exists as hydrogen molecule. A molecule of a compound is made out of two or more elements. A covalent bond is a chemical bond that involves the sharing of electron pairs between atoms. These electron pairs are
Molecule
which occurs regularly during the ion implantation doping of silicon chips. The defects production can be harmful, such as in nuclear fission and fusion reactors where the neutrons slowly degrade the mechanical properties of the materials, or a useful and desired materials modification effect, e.g., when ions are introduced into semiconductor quantum well structures to speed up the operation of a laser. or to strengthen carbon nanotubes. A curious feature of collision cascades is that the final amount of damage produced may be much less than the number of atoms initially affected by the heat spikes. Especially in pure metals,
Collision cascade
target ion in this case is divalent, Cu. This ion is classified as borderline in the scheme of Ahrland, Chatt and Davies. This means that it forms roughly equally strong complexes with ligands whose donor atoms are N, O or F as with ligands whose donor atoms are P, S or Cl. Penicillamine, which contains nitrogen and sulphur donor atoms, is used as this type of ligand binds more strongly to copper ions than to calcium and magnesium ions. Treatment of poisoning by heavy metals such as lead and mercury is more problematical, because the ligands used do not have
Binding selectivity
Alkalide An alkalide is a chemical compound in which alkali metal atoms are anions (negative ions) with a charge or oxidation state of –1. Until the first discovery of alkalides in the 1970s, alkali metals were only known to appear in salts only as cations (positive ions) with a charge or oxidation state of +1. These types of compounds are of theoretical interest due to their unusual stoichiometry and low ionization potentials. Alkalide compounds are chemically related to the electrides, salts in which trapped electrons are effectively the anions. Alkali metals form many well-known stable salts. Sodium chloride (common table
Alkalide
atom or using several atoms. Examples of such polyatomic ligands are the oxoanions CO and the related carboxylates, PO, and the polyoxometalates. Several organophosphorus ligands have been developed that bridge pairs of metals, a well-known example being PhPCHPPh. Bridging ligand In coordination chemistry, a bridging ligand is a ligand that connects two or more atoms, usually metal ions. The ligand may be atomic or polyatomic. Virtually all complex organic compounds can serve as bridging ligands, so the term is usually restricted to small ligands such as pseudohalides or to ligands that are specifically designed to link two metals. In naming
Bridging ligand
d-orbital bonding, have higher cohesive energies (i.e. they are more weakly bonded) than all transition metals, including Cu, and are therefore useful as high-energy anode metals. The difference between the metals' ionization energies in water is the other energetic contribution that can drive the reaction in a galvanic cell; it is not important in the Daniell cell because the energies of hydrated Cu and Zn ions happen to be similar. Both atom transfer, e.g. of zinc from the metal electrode into the solution, and electron transfer, from metal atoms or to metal ions, play important roles in a galvanic cell.
Galvanic cell
stronger complexes with ligands whose donor atoms are [[nitrogen]], [[oxygen]] or [[fluorine]] than with ligands whose donor atoms are [[phosphorus]], [[sulfur]] or [[chlorine]] and class B if the reverse is true. For example, Ni forms stronger complexes with [[amine]]s than with [[phosphines]], but Pd forms stronger complexes with phosphines than with amines. Later, Pearson proposed the theory of [[HSAB theory|hard and soft acids and bases]] (HSAB theory). In this classification, class A metals are hard acids and class B metals are soft acids. Some ions, such as copper(I), are classed as borderline. Hard acids form stronger complexes with hard bases
Stability constants of complexes
used as nodes. Partially filled d orbitals, either in the atom or ion, can hybridize differently depending on environment. This electronic structure causes some of them to exhibit multiple coordination geometries, particularly copper and gold ions which as neutral atoms have full d-orbitals in their outer shells. Lanthanides are large atoms with coordination numbers varying from 7 to 14. Their coordination environment can be difficult to predict, making them challenging to use as nodes. They offer the possibility of incorporating luminescent components. Alkali metals and alkaline earth metals exist as stable cations. Alkali metals readily form cations with stable valence
Coordination polymer
occur when the metal oxidation state is high. An example is provided by the molybdenum(IV) complex [MoO(HO)] in which there is a triangle of molybdenum atoms joined by σ- bonds with an oxide bridge on each edge of the triangle and a fourth oxide which bridges to all three Mo atoms. There are very few oxo-aqua ions of metals in the oxidation state +5 or higher. Rather, the species found in aqueous solution are monomeric and polymeric oxyanions. Oxyanions can be viewed as the end products of hydrolysis, in which there are no water molecules attached to the metal, only
Metal ions in aqueous solution
metals decreases down the group. This is because metal atoms are held together by the electromagnetic attraction from the positive ions to the delocalised electrons. As the atoms increase in size going down the group (because their atomic radius increases), the nuclei of the ions move further away from the delocalised electrons and hence the metallic bond becomes weaker so that the metal can more easily melt and boil, thus lowering the melting and boiling points. (The increased nuclear charge is not a relevant factor due to the shielding effect.) The alkali metals all have the same crystal structure (body-centred
Alkali metal
to often bind to two or three metals simultaneously. Atoms that bridge metals are sometimes indicated with the prefix ""μ"". Most inorganic solids are polymers by virtue of the presence of multiple bridging ligands. Bridging ligands, capable of coordinating multiple metal ions, have been attracting considerable interest because of their potential use as building blocks for the fabrication of functional multimetallic assemblies. Binucleating ligands bind two metals. Usually binucleating ligands feature bridging ligands, such as phenoxide, pyrazolate, or pyrazine, as well as other donor groups that bind to only one of the two metals. Some ligands can bond to a
Ligand
and below the plane of the Y. If more argon atoms are added they line up with the hydrogen atoms. Δ"H" for ArCH is 11 kcal/mol, and for ArCH it is 13.5 kcal/mol (for 2Ar + CH). Dications with argon are known for the coinage metals. Known dications include CuAr and AgAr for n=1-8, with a peak occurrence of CuAr, or AgAr, and AuAr n=3-7. In addition to the four argon atoms, the six argon atoms clusters have enhanced concentration. The stability of the ions with two positive charges is unexpected as the ionization energy of argon is lower than
Argon compounds
units, which contain nitrogen donor atoms. Each metal atom is six-coordinate, bonded to two other metals along the axis of the molecule (except terminal metals, which are bonded to one metal and one capping anion) and to four nitrogen atoms perpendicular to the axis. The organic ligands template the formation of the chains by bringing the metal ions together and aligning them into a linear string. The number of nitrogen atoms in the ligand determines the number of metal atoms that will be incorporated into the chain. Thus, the synthesis yields molecular wires of predetermined length. This feature, in combination
Extended metal atom chains
Bridging ligand In coordination chemistry, a bridging ligand is a ligand that connects two or more atoms, usually metal ions. The ligand may be atomic or polyatomic. Virtually all complex organic compounds can serve as bridging ligands, so the term is usually restricted to small ligands such as pseudohalides or to ligands that are specifically designed to link two metals. In naming a complex wherein a single atom bridges two metals, the bridging ligand is preceded by the Greek character 'mu', μ, with a subscript number denoting the number of metals bound to the bridging ligand. μ is often denoted
Bridging ligand
"half-filled or completely filled subshells are particularly stable arrangements of electrons". The apparent paradox arises when electrons are "removed" from the transition metal atoms to form ions. The first electrons to be ionized come not from the 3d-orbital, as one would expect if it were "higher in energy", but from the 4s-orbital. This interchange of electrons between 4s and 3d is found for all atoms of the first series of transition metals. The configurations of the neutral atoms (K, Ca, Sc, Ti, V, Cr, ...) usually follow the order 1s, 2s, 2p, 3s, 3p, 4s, 3d, ...; however the successive
Electron configuration
that make it up. This charge is often small, because matter is made of atoms, and atoms typically have equal numbers of protons and electrons, in which case their charges cancel out, yielding a net charge of zero, thus making the atom neutral. An "ion" is an atom (or group of atoms) that has lost one or more electrons, giving it a net positive charge (cation), or that has gained one or more electrons, giving it a net negative charge (anion). "Monatomic ions" are formed from single atoms, while "polyatomic ions" are formed from two or more atoms that have
Electric charge
ions in neighbouring reactants can diffuse together during the time the reactant mixture remains in the oven. Other synthetic routes use a solid precursor with the correct stoichiometric ratio of non-volatile ions, which is heated to drive off other species. In some reactions between highly reactive metals (usually from Group 1 or Group 2) and highly electronegative halogen gases, or water, the atoms can be ionized by electron transfer, a process thermodynamically understood using the Born–Haber cycle. Ions in ionic compounds are primarily held together by the electrostatic forces between the charge distribution of these bodies, and in particular the
Ionic compound
are constrained relative to each other, thereby resulting in the bond being characteristically brittle. Metallic bonding can be classified as a type of covalent bonding for which the constituent atoms of the same type and do not combine with one another to form a chemical bond. Atoms will lose an electron(s) forming an array of positive ions. These electrons are shared by the lattice which makes the electron cluster mobile, as the electrons are free to move as well as the ions. For this, it gives metals their relatively high thermal and electrical conductivity as well as being characteristically ductile.
Welding
theoretically able to break most covalent bonds including the C–O bonds in a typical cryptand. The introduction of a special cryptand ligand containing amines instead of ether linkages has allowed the isolation of kalides and natrides that are stable at room temperature. Several alkalides have been synthesized: Alkalide An alkalide is a chemical compound in which alkali metal atoms are anions (negative ions) with a charge or oxidation state of –1. Until the first discovery of alkalides in the 1970s, alkali metals were only known to appear in salts only as cations (positive ions) with a charge or oxidation state
Alkalide
for fluorine's easy dissociation, high reactivity, and strong bonds to non-fluorine atoms. Conversely, bonds to other atoms are very strong because of fluorine's high electronegativity. Unreactive substances like powdered steel, glass fragments, and asbestos fibers react quickly with cold fluorine gas; wood and water spontaneously combust under a fluorine jet. Reactions of elemental fluorine with metals require varying conditions. Alkali metals cause explosions and alkaline earth metals display vigorous activity in bulk; to prevent passivation from the formation of metal fluoride layers, most other metals such as aluminium and iron must be powdered, and noble metals require pure fluorine gas
Fluorine
SIMS that allowed for the primary beam to no longer cause damaging effects to the sample. The major difference between the two techniques is the difference in the nature of the primary beam used; ions vs atoms. For LSIMS, Cesium, Cs ions make up the primary beam and for FAB the primary beam is made up of Xe or Ar atoms. Xe atoms are used because they tend to be more sensitive than Argon atoms due to their larger masses and more momentum. For the molecules to be ionized by FAB, first the slow moving atoms (Xe or Ar) are
Fast atom bombardment
a significant portion of the fields of solid-state chemistry, physics, materials science and engineering. Metallic solids are held together by a high density of shared, delocalized electrons, known as "metallic bonding". In a metal, atoms readily lose their outermost ("valence") electrons, forming positive ions. The free electrons are spread over the entire solid, which is held together firmly by electrostatic interactions between the ions and the electron cloud. The large number of free electrons gives metals their high values of electrical and thermal conductivity. The free electrons also prevent transmission of visible light, making metals opaque, shiny and lustrous. More
Solid
the linear combination of atomic orbitals (LCAO) helps describe the delocalized molecular orbital structures and energies based on the atomic orbitals of the atoms they came from. Unlike pure ionic bonds, covalent bonds may have directed anisotropic properties. These may have their own names, such as sigma bond and pi bond. In the general case, atoms form bonds that are intermediate between ionic and covalent, depending on the relative electronegativity of the atoms involved. This type of bond is sometimes called polar covalent. Chemical bond A chemical bond is a lasting attraction between atoms, ions or molecules that enables the
Chemical bond
which is similar to trivalent lanthanide metals but smaller than more familiar metals, such as aluminium (70 GPa). Californium exhibits oxidation states of 4, 3, or 2. It typically forms eight or nine bonds to surrounding atoms or ions. Its chemical properties are predicted to be similar to other primarily 3+ valence actinide elements and the element dysprosium, which is the lanthanide above californium in the periodic table. The element slowly tarnishes in air at room temperature, with the rate increasing when moisture is added. Californium reacts when heated with hydrogen, nitrogen, or a chalcogen (oxygen family element); reactions with
Californium
called clean-up. The gas atoms or molecules are adsorbed on the surfaces of the electrodes. In high voltage tubes, the accelerated ions can penetrate into the electrode materials. New surfaces, formed by sputtering of the electrodes and deposited on e.g. the inner surfaces of the tube, also readily adsorb gases. Non-inert gases can also chemically react with the tube components. Hydrogen may diffuse through some metals. For removal of gas in vacuum tubes, getters are used. For resupplying gas for gas-filled tubes, replenishers are employed. Most commonly, replenishers are used with hydrogen; a filament made from a hydrogen-absorbing metal (e.g.
Gas-filled tube
matter is primarily ionized, and the density may be as low as 10 ions per cm. Compare this with a number density of roughly 10 molecules per cm for air at sea level, and 10 molecules per cm (10 billion molecules per cm) for a laboratory high-vacuum chamber. By mass, 99% of the ISM is gas in any form, and 1% is dust. Of the gas in the ISM, by number 91% of atoms are hydrogen and 8.9% are helium, with 0.1% being atoms of elements heavier than hydrogen or helium, known as "metals" in astronomical parlance. By mass this
Interstellar medium
rust. Only iron or alloys that contain iron can rust, but other metals can corrode in similar ways. The main catalyst for the rusting process is water. Iron or steel structures might appear to be solid, but water molecules can penetrate the microscopic pits and cracks in any exposed metal. The hydrogen atoms present in water molecules can combine with other elements to form acids, which will eventually cause more metal to be exposed. If chloride ions are present, as is the case with saltwater, the corrosion is likely to occur more quickly. Meanwhile, the oxygen atoms combine with metallic
Rust
either dilute or concentrated nitric, hydrochloric or sulfuric acids, but easily dissolves in hydrofluoric acid. The dioxide can be converted back to pentoxide by heating in oxygen-containing atmosphere to 1100 °C. The monoxide PaO has only been observed as a thin coating on protactinium metal, but not in an isolated bulk form. Protactinium forms mixed binary oxides with various metals. With alkali metals "A", the crystals have a chemical formula APaO and perovskite structure, or APaO and distorted rock-salt structure, or APaO where oxygen atoms form a hexagonal close-packed lattice. In all these materials, protactinium ions are octahedrally coordinated. The
Protactinium
the newly developed technique, flame spectroscopy. Rubidium's compounds have various chemical and electronic applications. Rubidium metal is easily vaporized and has a convenient spectral absorption range, making it a frequent target for laser manipulation of atoms. Rubidium is not a known nutrient for any living organisms. However, rubidium ions have the same charge as potassium ions, and are actively taken up and treated by animal cells in similar ways. Rubidium is a very soft, ductile, silvery-white metal. It is the second most electropositive of the stable alkali metals and melts at a temperature of . Like other alkali metals, rubidium
Rubidium
a halogen, never existing in pure form in nature. Bromine is barely liquid at room temperature, boiling at about 330 kelvins. Bromine is also quite toxic and corrosive, but bromide ions, which are relatively inert, can be found in halite, or table salt. Bromine is often used as a fire retardant because many compounds can be made to release free bromine atoms. Krypton (Kr) is a noble gas, placed under argon and over xenon. Being a noble gas, krypton rarely interacts with itself or other elements; although compounds have been detected, they are all unstable and decay rapidly, and as
Period 4 element
will now have a valence of 1.1. Most lattice sites however are still occupied by silver atoms and consequently the changes in electronic structure are minimal. In a pure metal of valence Z, all atoms become positive ions with the valence +Z by releasing the outermost Z electrons per atom to form the valence band. As a result, conduction electrons carrying negative charges are uniformly distributed over any atomic site with equal probability densities and maintain charge neutrality with the array of ions with positive charges. When an impurity atom of valence Z is introduced, the periodic potential is disturbed,
Rigid-band model
into electrical energy. A simple cell does this by using a combination of two metals (electrodes) and an electrolyte solution (which could be acid/alkali/salt solution). Metals can conduct electricity due to metallic bonding. Metallic bonds are the electrostatic force of attraction between negatively charged delocalised electrons and the positively charged metal ions. Metal atoms are surrounded by a “sea” of delocalised electrons. This means they are free to move within the structure- this gives metals its conducting abilities as an electric current can flow through it. A reaction between metals where electrons are gained is called a reduction reaction A
Electrochemical cell
freely-moving or delocalization of bonding electrons leads to classical metallic properties such as luster (surface light reflectivity), electrical and thermal conductivity, ductility, and high tensile strength. There are four basic types of bonds that can be formed between two or more (otherwise non-associated) molecules, ions or atoms. Intermolecular forces cause molecules to be attracted or repulsed by each other. Often, these define some of the physical characteristics (such as the melting point) of a substance. In the (unrealistic) limit of "pure" ionic bonding, electrons are perfectly localized on one of the two atoms in the bond. Such bonds can be
Chemical bond
towards the electron-providing (negative) cathode. Negatively charged ions (anions) move towards the electron-extracting (positive) anode. In this process electrons are either absorbed or released. Neutral atoms gain or lose electrons and become charged ions that then pass into the electrolyte. The formation of uncharged atoms from ions is called discharging. When an ion gains or loses enough electrons to become uncharged (neutral) atoms, the newly formed atoms separate from the electrolyte. Positive metal ions like Cudeposit onto the cathode in a layer. The terms for this are electroplating, electrowinning, and electrorefining. When an ion gains or loses electrons without becoming
Electrolysis
use of quantum statistics. Materials that are called "paramagnets" are most often those that exhibit, at least over an appreciable temperature range, magnetic susceptibilities that adhere to the Curie or Curie–Weiss laws. In principle any system that contains atoms, ions, or molecules with unpaired spins can be called a paramagnet, but the interactions between them need to be carefully considered. The narrowest definition would be: a system with unpaired spins that "do not interact" with each other. In this narrowest sense, the only pure paramagnet is a dilute gas of monatomic hydrogen atoms. Each atom has one non-interacting unpaired electron.
Paramagnetism
Trigonal prismatic molecular geometry In chemistry, the trigonal prismatic molecular geometry describes the shape of compounds where six atoms, groups of atoms, or ligands are arranged around a central atom, defining the vertices of a triangular prism. Hexamethyltungsten (W(CH)) was the first example of a molecular trigonal prismatic complex. The figure shows the six carbons arranged at the vertices of a triangular prism with the tungsten at the centre. The hydrogens are not shown. Some other transition metals have trigonal prismatic hexamethyl complexes, including both neutral molecules such as Mo(CH) and Re(CH) and ions such as and . The complex
Trigonal prismatic molecular geometry
earlier. Since 1952, elements 101 (mendelevium) to 117 (tennessine) have been synthesized. The most recently synthesized element is 118 (oganneson). Its status as a metal or a nonmetal—or something else—is not yet clear. A metallic glass (also known as an amorphous or glassy metal) is a solid metallic material, usually an alloy, with disordered atomic-scale structure. Most pure and alloyed metals, in their solid state, have atoms arranged in a highly ordered crystalline structure. Amorphous metals have a non-crystalline glass-like structure. But unlike common glasses, such as window glass, which are typically electrical insulators, amorphous metals have good electrical conductivity.
Metal
exemplified by the Embedded atom model. This typically results in metals assuming relatively simple, close-packed crystal structures, such as FCC, BCC, and HCP. Given high enough cooling rates and appropriate alloy composition, metallic bonding can occur even in glasses with an amorphous structure. Much biochemistry is mediated by the weak interaction of metal ions and biomolecules. Such interactions and their associated conformational change has been measured using dual polarisation interferometry. Metals are insoluble in water or organic solvents unless they undergo a reaction with them. Typically this is an oxidation reaction that robs the metal atoms of their itinerant electrons,
Metallic bonding
covalently-bound pairs of atoms in both liquid and solid state—these pairs form a crystal structure with metallic bonding between them. Another example of a metal–metal covalent bond is mercurous ion (). As chemistry developed into a science it became clear that metals formed the large majority of the periodic table of the elements and great progress was made in the description of the salts that can be formed in reactions with acids. With the advent of electrochemistry, it became clear that metals generally go into solution as positively charged ions and the oxidation reactions of the metals became well understood
Metallic bonding
molecule, which decomposes to produce the corresponding hydrocarbon (hydrogen atoms substitute the original chlorine atoms) and free chloride ions. For instance, the reductive dechlorination of CFCs is complete and produces several HFCs plus chloride. Hydrodechlorination (HDC) is a type of reductive dechlorination that is useful due to its high reaction rate. It uses H as the reducing agent over a range of potential electrode reactors and catalysts. Amongst the types of catalysts studied such as precious metals (Pt, Pd, Rh), transition metals (Ni and Mo), and metal oxides, a preference for precious metals overrides the others.As an example, palladium (Pd)
Reductive dechlorination
discharge is composed of ions, ground state atoms, and fraction of excited atoms. When the excited atoms relax back into their ground state, a low-intensity glow is emitted, giving the technique its name. The requirement for samples of glow discharge atomizers is that they are electrical conductors. Consequently, atomizers are most commonly used in the analysis of metals and other conducting samples. However, with proper modifications, it can be utilized to analyze liquid samples as well as nonconducting materials by mixing them with a conductor (e.g. graphite). Hydride generation techniques are specialized in solutions of specific elements. The technique provides
Atomic absorption spectroscopy
crystals of ammonium iron formate (NHFe(HCOO)) and ammonium nickel formate (NHNi(HCOO)) at 1.5 GPa to yield Ne•NHFe(HCOO) and Ne•NHNi(HCOO). The neon atoms become trapped in a cage of five metal triformate units. The windows in the cages are blocked by ammonium ions. Argon does not undergo this, probably as its atoms are too big. Ionic molecules can include neon, such as the clusters where "m" goes from 1 to 7 and "n" from 1 to over 20. HeNe (helium neide) has a relatively strong covalent bond. The charge is distributed across both atoms. When metals are evaporated into a thin
Neon compounds
only been observed for certain target species and requires a minimum potential energy. Removing atoms by sputtering with an inert gas is called "ion milling" or "ion etching". Sputtering can also play a role in reactive-ion etching (RIE), a plasma process carried out with chemically active ions and radicals, for which the sputtering yield may be enhanced significantly compared to pure physical sputtering. Reactive ions are frequently used in secondary ion mass spectrometry (SIMS) equipment to enhance the sputter rates. The mechanisms causing the sputtering enhancement are not always well understood, although the case of fluorine etching of Si has
Sputtering
of hexagonally close packed atoms. In both of these very similar lattices there are two sorts of interstice, or hole: It was suggested by early workers that: These were not viewed as compounds, but rather as solutions, of say carbon, in the metal lattice, with a limiting upper “concentration” of the smaller atom that was determined by the number of interstices available. A more detailed knowledge of the structures of metals, and binary and ternary phases of metals and non metals shows that: One example is the solubility of carbon in iron. The form of pure iron stable between 910
Interstitial compound
Acid salt Acid salts are a class of salts that produce an acidic solution after being dissolved in a solvent. Its formation as a substance has a greater electrical conductivity than that of the pure solvent. An acidic solution formed by acid salt is made during partial neutralization of diprotic or polyprotic acids. A "half-neutralization" occurs due to the remaining of replaceable hydrogen atoms from the partial dissociation of weak acids that have not been reacted with hydroxide ions (OH) to create water molecules. Acid salt is an ionic compound consisted of an anion, contributed from a weak parent acid,
Acid salt
Stannide A stannide can refer to an intermetallic compound containing tin combined with one or more other metals; an anion consisting solely of tin atoms or a compound containing such an anion, or, in the field of organometallic chemistry an ionic compound containing an organotin anion (e.g.see an alternative name for such a compound is stannanide.) When tin is combined with an alkali or alkaline earth metal some of the compounds formed have ionic structures containing monatomic or polyatomic tin anions (Zintl ions), such as Sn in MgSn or in KSn. Even with these metals not all of the compounds
Stannide
crystallography has proven possible even for viruses and proteins with hundreds of thousands of atoms, through improved crystallographic imaging and technology. Though normally X-ray crystallography can only be performed if the sample is in crystal form, new research has been done into sampling non-crystalline forms of samples. Although crystallography can be used to characterize the disorder in an impure or irregular crystal, crystallography generally requires a pure crystal of high regularity to solve the structure of a complicated arrangement of atoms. Pure, regular crystals can sometimes be obtained from natural or synthetic materials, such as samples of metals, minerals or
X-ray crystallography
wire, usually platinum. The heat from the flame evaporates the solvent and breaks chemical bonds to create free atoms. The thermal energy also excites the atoms into excited electronic states that subsequently emit light when they return to the ground electronic state. Each element emits light at a characteristic wavelength, which is dispersed by a grating or prism and detected in the spectrometer. A frequent application of the emission measurement with the flame is the regulation of alkali metals for pharmaceutical analytics. Inductively coupled plasma atomic emission spectroscopy (ICP-AES) uses an inductively coupled plasma to produce excited atoms and ions
Atomic emission spectroscopy
to the use of a different method for defining and counting the hydrogen bonds. Where the bond strengths are more equivalent, one might instead find the atoms of two interacting water molecules partitioned into two polyatomic ions of opposite charge, specifically hydroxide (OH) and hydronium (HO). (Hydronium ions are also known as "hydroxonium" ions.) Indeed, in pure water under conditions of standard temperature and pressure, this latter formulation is applicable only rarely; on average about one in every 5.5 × 10 molecules gives up a proton to another water molecule, in accordance with the value of the dissociation constant for
Hydrogen bond
sparks and arcs are usually undesirable, they can be useful in applications such as spark plugs for gasoline engines, electrical welding of metals, or for metal melting in an electric arc furnace. Prior to gas discharge the gas glows with distinct colors that depend on the energy levels of the atoms. Not all mechanisms are fully understood. The vacuum itself is expected to undergo electrical breakdown at or near the Schwinger limit. Before gas breakdown, there is a non-linear relation between voltage and current as shown in the figure. In region 1, there are free ions that can be accelerated
Electrical breakdown
Spectroscopy of multiply ionized atoms This branch of spectroscopy deals with radiation related to atoms that are stripped of several electrons (multiply ionized atoms (MIA), multiply charged ions, highly charged ions). These are observed in very hot plasmas (laboratory or astrophysical) or in accelerator experiments (beam-foil, electron beam ion trap (EBIT)). The lowest exited electron shells of such ions decay into stable ground states producing photons in VUV, EUV and soft X-ray spectral regions (so-called resonance transitions). After Newton's. discovery of spectral structure of white light (17th century) and subsequent studies of the nature of light (Hooke, Huygens, Young) J.
Spectroscopy of multiply ionized atoms
octupole decay, lifetimes of forbidden transitions, charge-exchange recombination, etc. Spectroscopy of multiply ionized atoms This branch of spectroscopy deals with radiation related to atoms that are stripped of several electrons (multiply ionized atoms (MIA), multiply charged ions, highly charged ions). These are observed in very hot plasmas (laboratory or astrophysical) or in accelerator experiments (beam-foil, electron beam ion trap (EBIT)). The lowest exited electron shells of such ions decay into stable ground states producing photons in VUV, EUV and soft X-ray spectral regions (so-called resonance transitions). After Newton's. discovery of spectral structure of white light (17th century) and subsequent studies
Spectroscopy of multiply ionized atoms
that the collisions occur very close to each other. Then the binary collision approximation is no longer valid, but rather the collisional process should be understood as a many-body process. The dense collisions induce a heat spike (also called thermal spike), which essentially melts the crystal locally. If the molten zone is close enough to a surface, large numbers of atoms may sputter due to flow of liquid to the surface and/or microexplosions. Heat spike sputtering is most important for heavy ions (e.g. Xe or Au or cluster ions) with energies in the keV–MeV range bombarding dense but soft metals
Sputtering
more clearly. For instance, zinc and cadmium are similar to beryllium and magnesium in their atomic radii, ionic radii, electronegativities, and also in the structure of their binary compounds and their ability to form complex ions with many nitrogen and oxygen ligands, such as complex hydrides and amines. However, beryllium and magnesium are small atoms, unlike the heavier alkaline earth metals and like the group 12 elements (which have a greater nuclear charge but the same number of valence electrons), and the periodic trends down group 2 from beryllium to radium (similar to that of the alkali metals) are not
Group 12 element
by electron ionization, for instance noble gases (Ar, Xe), oxygen (O, O, O), or even ionized molecules such as SF (generated from SF) or C (fullerene). This type of ion gun is easy to operate and generates roughly focused but high current ion beams. A second source type, the surface ionization source, generates Cs primary ions. Cesium atoms vaporize through a porous tungsten plug and are ionized during evaporation. Depending on the gun design, fine focus or high current can be obtained. A third source type, the liquid metal ion gun (LMIG), operates with metals or metallic alloys, which are
Secondary ion mass spectrometry
has much covalent character. The hydroxide ion displays cylindrical symmetry in hydroxides of divalent metals Ca, Cd, Mn, Fe, and Co. For example, magnesium hydroxide Mg(OH) (brucite) crystallizes with the cadmium iodide layer structure, with a kind of close-packing of magnesium and hydroxide ions. The amphoteric hydroxide Al(OH) has four major crystalline forms: gibbsite (most stable), bayerite, nordstrandite, and doyleite. All these polymorphs are built up of double layers of hydroxide ions – the aluminium atoms on two-thirds of the octahedral holes between the two layers – and differ only in the stacking sequence of the layers. The structures are
Hydroxide
structure each sodium atom has six near neighbour chloride ions in an octahedral geometry and each chloride has similarly six near neighbour sodium ions in an octahedral geometry. In metals with the body centred cubic (bcc) structure each atom has eight nearest neighbours in a cubic geometry. In metals with the face centred cubic (fcc) structure each atom has twelve nearest neighbours in a cuboctahedral geometry. A table of the coordination geometries encountered is shown below with examples of their occurrence in complexes found as discrete units in compounds and coordination spheres around atoms in crystals (where there is no
Coordination geometry
compounds "MX" of transition metals "M" and chalcogens "X" = O, S, Se and Te. Also certain dipnictides with "X" standing for P, As and Sb etc. are known to adopt the pyrite structure. In the first bonding sphere, the Fe atoms are surrounded by six S nearest neighbours, in a distorted octahedral arrangement. The material is a diamagnetic semiconductor and the Fe ions should be considered to be in a "low spin" divalent state (as shown by Mössbauer spectroscopy as well as XPS), rather than a tetravalent state as the stoichiometry would suggest. The positions of "X" ions in
Pyrite
been bonded together, in each case yielding an ion with a positive or negative net charge. During formation of macroscopic objects, constituent atoms and ions usually combine to form structures composed of neutral "ionic compounds" electrically bound to neutral atoms. Thus macroscopic objects tend toward being neutral overall, but macroscopic objects are rarely perfectly net neutral. Sometimes macroscopic objects contain ions distributed throughout the material, rigidly bound in place, giving an overall net positive or negative charge to the object. Also, macroscopic objects made of conductive elements, can more or less easily (depending on the element) take on or give
Electric charge
bonding sometimes can be described using polyhedral skeletal electron pair theory (Wade's rules) where the number of valence electrons contributed by each tin atom is considered to be 2 (the s electrons do not contribute). There are some examples of silicide and plumbide ions with similar structures, for example tetrahedral , the chain anion (Si), and . Stannide A stannide can refer to an intermetallic compound containing tin combined with one or more other metals; an anion consisting solely of tin atoms or a compound containing such an anion, or, in the field of organometallic chemistry an ionic compound containing
Stannide
sodium may substitute for pure sodium in fast breeder nuclear reactors. Rubidium and caesium are often used in atomic clocks. Caesium atomic clocks are extraordinarily accurate; if a clock had been made at the time of the dinosaurs, it would be off by less than four seconds (after 80 million years). For that reason, caesium atoms are used as the definition of the second. Rubidium ions are often used in purple fireworks, and caesium is often used in drilling fluids in the petroleum industry. Francium has no commercial applications, but because of francium's relatively simple atomic structure, among other things,
Alkali metal
argon and then form a cluster ion when the rest of the droplet evaporates. NeHe can be made by ultraviolet photoionisation. Clusters only contain one neon atom. The number of helium atoms n can vary from 1 to 23, but NeHe and NeHe are more likely to be observed. Doubly charged ions of helium with noble gas atoms also exist including ArHe, KrHe, and XeHe. Various metal-helium ions are known. Alkali metal helide ions are known for all the alkalis. The molecule ground state for the diatomic ions is in the XΣ state. The bond length gets bigger as the
Helium compounds
standard activity is measured, to provide a baseline for comparison. AMS counts the atoms of and in a given sample, determining the / ratio directly. The sample, often in the form of graphite, is made to emit C ions (carbon atoms with a single negative charge), which are injected into an accelerator. The ions are accelerated and passed through a stripper, which removes several electrons so that the ions emerge with a positive charge. The ions, which may have from 1 to 4 positive charges (C to C), depending on the accelerator design, are then passed through a magnet that
Radiocarbon dating
(i.e. no pressurised tanks nor valves are required). Moreover, alkali metals have the lowest attitude to form ionized droplets or multiply-charged ions, thus leading to the best attainable mass efficiency. The actual thrust is produced by exhausting a beam of mainly singly-ionized cesium or rubidium atoms, produced by field evaporation at the tip of the emitter. An accelerating electrode (accelerator) is placed directly in front of the emitter. This electrode consists of a metal (usually stainless steel) plate where two sharp blades are machined. When thrust is required, a strong electric field is generated by the application of a high
Field-emission electric propulsion
Sympathetic cooling Sympathetic cooling is a process in which particles of one type cool particles of another type. Typically, atomic ions that can be directly laser cooled are used to cool nearby ions or atoms, by way of their mutual Coulomb interaction. This technique allows cooling of ions and atoms that can't be cooled directly by laser cooling. This includes most molecular ion species, especially large organic molecules. However, sympathetic cooling is most efficient when the mass/charge ratios of the sympathetic- and laser-cooled ions are similar. The cooling of neutral atoms in this manner was first demonstrated by Christopher Myatt
Sympathetic cooling
by gamma rays. The positive ions are driven towards the cathode by the electric potential, and the electrons are driven towards the anode by the same potential. The initial population of ions and electrons collides with other atoms, exciting or ionizing them. As long as the potential is maintained, a population of ions and electrons remains. Some of the ions' kinetic energy is transferred to the cathode. This happens partially through the ions striking the cathode directly. The primary mechanism, however, is less direct. Ions strike the more numerous neutral gas atoms, transferring a portion of their energy to them.
Glow discharge
combined into one substance through a chemical reaction form a chemical compound. All compounds are substances, but not all substances are compounds. A chemical compound can be either atoms bonded together in molecules or crystals in which atoms, molecules or ions form a crystalline lattice. Compounds based primarily on carbon and hydrogen atoms are called organic compounds, and all others are called inorganic compounds. Compounds containing bonds between carbon and a metal are called organometallic compounds. Compounds in which components share electrons are known as covalent compounds. Compounds consisting of oppositely charged ions are known as ionic compounds, or salts.
Chemical substance
for high-temperature solid-state synthesis. Many metals are geologically most abundant as ionic compounds within ores. To obtain the elemental materials, these ores are processed by smelting or electrolysis, in which redox reactions occur (often with a reducing agent such as carbon) such that the metal ions gain electrons to become neutral atoms. According to the nomenclature recommended by IUPAC, ionic compounds are named according to their composition, not their structure. In the most simple case of a binary ionic compound with no possible ambiguity about the charges and thus the stoichiometry, the common name is written using two words. The
Ionic compound
discrete with the period of the potential. The ions in a perfect crystal are arranged in a regular periodic array. So we are led to the problem of an electron in a potential formula_131 with the periodicity of the underlying Bravais lattice for all Bravais lattice vectors formula_133 However, perfect periodicity is an idealisation. Real solids are never absolutely pure, and in the neighbourhood of the impurity atoms the solid is not the same as elsewhere in the crystal. Moreover, the ions are not in fact stationary, but continually undergo thermal vibrations about their equilibrium positions. These destroy the perfect
Translation operator (quantum mechanics)
of the charge is omitted for singly charged molecules/atoms; for example, the sodium cation is indicated as Na and "not" Na. An alternative (and acceptable) way of showing a molecule/atom with multiple charges is by drawing out the signs multiple times, this is often seen with transition metals. Chemists sometimes circle the sign; this is merely ornamental and does not alter the chemical meaning. All three representations of shown in the figure, are thus equivalent. Monatomic ions are sometimes also denoted with Roman numerals; for example, the example seen above is occasionally referred to as Fe(II) or Fe. The Roman
Ion
identical CX1159 has 33 kV. Also, at the same voltage the pressure of deuterium can be higher than of hydrogen, allowing higher rise rates of rise of current before it causes excessive anode dissipation. Significantly higher peak powers are achievable. Its recovery time is however about 40% slower than for hydrogen. Noble gases are frequently used in tubes for many purposes, from lighting to switching. Pure noble gases are employed in switching tubes. Noble-gas-filled thyratrons have better electrical parameters than mercury-based ones. The electrodes undergo damage by high-velocity ions. The neutral atoms of the gas slow the ions down by
Gas-filled tube
fact, transition metal chalcogenides are highly covalent, not ionic, as indicated by their semiconducting properties. In most of their chalcogenides, transition metals adopt oxidation states of II or greater. Nonetheless, several examples exist where the metal/chalcogenide ratio is far less than one. Such compounds typically have extensive metal-metal bonding. Metal monochalcogenides have the formula ME, where M = a transition metal and E = S, Se, Te. They typically crystallize in one of two motifs, named after the corresponding forms of zinc sulfide. In the zinc blende structure, the sulfide atoms pack in a cubic symmetry and the Zn ions
Chalcogenide
atoms to form the destructive oxide compound. As the atoms combine, they weaken the metal, making the structure brittle and crumbly. When impure (cast) iron is in contact with water, oxygen, other strong oxidants, or acids, it rusts. If salt is present, for example in seawater or salt spray, the iron tends to rust more quickly, as a result of electrochemical reactions. Iron metal is relatively unaffected by pure water or by dry oxygen. As with other metals, like aluminium, a tightly adhering oxide coating, a passivation layer, protects the bulk iron from further oxidation. The conversion of the passivating
Rust
part of the total production. Consequently, scientific research has intensified on causes of brown color in diamond and ways to alter it. Irradiation of diamond by high-energy particles (electrons, ions, neutrons or gamma rays) produces vacancies in the diamond lattice by ejecting carbon atoms. Those vacancies produce green color centers in pure transparent diamond and yellow-green color in yellow diamonds. The color of yellow diamonds results from small numbers of nitrogen atoms replacing carbon in the lattice. Heating the irradiated diamonds to temperatures above 600 °C results in brown color associated with aggregation of the vacancies, with or without nitrogen
Brown diamonds
portion of a pure chemical substance that has its unique set of chemical properties, that is, its potential to undergo a certain set of chemical reactions with other substances. However, this definition only works well for substances that are composed of molecules, which is not true of many substances (see below). Molecules are typically a set of atoms bound together by covalent bonds, such that the structure is electrically neutral and all valence electrons are paired with other electrons either in bonds or in lone pairs. Thus, molecules exist as electrically neutral units, unlike ions. When this rule is broken,
Chemistry
Magic number (chemistry) The concept of magic numbers in the field of chemistry refers to a specific property (such as stability) for only certain representatives among a distribution of species. It was first recognized by inspecting the intensity of mass-spectrometric signals of rare gas cluster ions. In case a gas condenses into clusters of atoms, the number of atoms in these clusters that are most likely to form varies between a few and hundreds. However, there are peaks at specific cluster sizes, deviating from a pure statistical distribution. Therefore, it was concluded that clusters of these specific numbers of rare
Magic number (chemistry)
sustained fusion reaction, it is usually necessary to use many methods to heat the plasma. Neutral Beam Injection (NBI) involves injecting a high energy beam of neutral atoms, typically hydrogen or deuterium, into the core of the plasma. These energetic atoms transfer their energy to the plasma, raising the overall temperature. The neutral atoms injected don't remain neutral. As the beam passes through the plasma, the atoms are ionized as they bounce off the ions in the plasma. Because the magnetic field inside the torus is bent into a circle, the fast ions are hoped to be confined in the
Madison Symmetric Torus
as either molybdenite, a crystalline mineral, or jordisite, a rare low temperature form of molybdenite. Molybdenite ore is processed by flotation to give relatively pure . The main contaminant is carbon. also arises by thermal treatment of virtually all molybdenum compounds with hydrogen sulfide or elemental sulfur and can be produced by metathesis reactions from molybdenum pentachloride. All forms of have a layered structure, in which a plane of molybdenum atoms is sandwiched by planes of sulfide ions. These three strata form a monolayer of MoS. Bulk MoS consists of stacked monolayers, which are held together by weak van der
Molybdenum disulfide
years later with the founding of a company to commercialize the technique. A model resonance ionization mass spectrometry (RIMS) set-up consists of a laser system (consisting of multiple lasers), sample from which the atoms are derived, and a suitable mass spectrometer which mass-selectively detects the photo ions created from resonance. In resonant ionization, atoms or molecules from ground state are excited to higher energy states by the resonant absorption of photons to produce ions. These ions are then monitored by appropriate detectors. In order to ensure a highly-efficient sensitivity and process saturation, the atomic or molecular beam must be formed
Resonance ionization
(NH ions in a sea of electrons) at very high pressures, such as inside gas giant planets such as Uranus and Neptune. Under normal conditions, ammonium does not exist as a pure metal, but does as an amalgam (alloy with mercury). Ammonium The ammonium cation is a positively charged polyatomic ion with the chemical formula . It is formed by the protonation of ammonia (NH). Ammonium is also a general name for positively charged or protonated substituted amines and quaternary ammonium cations (), where one or more hydrogen atoms are replaced by organic groups (indicated by R). The ammonium ion
Ammonium
Metallodendrimer A Metallodendrimer is a type of dendrimer with incorporated metal atoms. The development of this type of material is actively pursued in academia. The metal can be situated in the repeat unit, the core or at the extremities as end-group. Elements often encountered are palladium and platinum. These metals can form octahedral six-coordinate M(IV) linking units from organic dihalides and the corresponding 4-coordinate M(II) monomers. Ferrocene-containing dendrimers and dendrimers with cobaltocene and arylchromiumtricarbonyl units have been reported in end-functional dendrimers. Metallodendrimers can form as metal complexes with dendritic counter ions for example by hydrolysis of ester terminated PAMAM dendrimers
Metallodendrimer
0.6%. The growth was done using powdered lutetium(III) oxide and crushed sapphire feedstock with 2M potassium bicarbonate mineralizer with a thermal gradient of 610 - 640 ˚C. The lasing process involving aluminum garnet crystals is carried out by the dopant atoms, usually rare-earth metals, which take the place of a few atoms of the original metal in the crystal structure (in this case lutetium). The role of the unsubstituted atoms of lutetium, aluminum, and oxygen function as support for the dopant ions. Lutetium aluminium garnet Lutetium aluminum garnet (commonly abbreviated LuAG, molecular formula AlLuO) is an inorganic compound with a
Lutetium aluminium garnet
perchloric acid (HClO), sulfuric acid (HSO), and phosphoric acid (HPO) are common oxyacids that have been prepared as pure substances. Imidic acids are created by replacing =O with =NR in an oxyacid. An oxyacid molecule contains the structure X−O−H, where other atoms or atom groups can be connected to the central atom X. In a solution, such a molecule can be dissociated into ions in two distinct ways: If the central atom X is strongly electronegative, then it strongly attracts the electrons of the oxygen atom. In that case, the bond between the oxygen and hydrogen atom is weak, and
Oxyacid
Northwestern University reported the use of artificial intelligence to predict and evaluate samples of 20,000 different likely metallic glass alloys in a year. Their methods promise to speed up research and time to market for new amorphous metals alloys. Amorphous metal is usually an alloy rather than a pure metal. The alloys contain atoms of significantly different sizes, leading to low free volume (and therefore up to orders of magnitude higher viscosity than other metals and alloys) in molten state. The viscosity prevents the atoms moving enough to form an ordered lattice. The material structure also results in low shrinkage
Amorphous metal
of chlorine, and the reaction to monochlorides, may actually impair their color purity or intensity. At high temperatures, the atoms will ionize. The emission spectra of ions are different than of neutral atoms; the ions may emit in undesired spectral ranges. For example, Ba emits in blue wavelengths. Ionization can be suppressed by addition of an easier-to-ionize metal with weak visible emission of its own, e.g. potassium; the potassium atoms then act as electron donors, neutralizing the barium ions. The color blue is notoriously difficult to produce in fireworks, as the copper compounds need to be heated at a specific
Pyrotechnic colorant
massive as an electron. They were protons. The process by which anode rays are formed in a gas-discharge anode ray tube is as follows. When the high voltage is applied to the tube, its electric field accelerates the small number of ions (electrically charged atoms) always present in the gas, created by natural processes such as radioactivity. These collide with atoms of the gas, knocking electrons off of them and creating more positive ions. These ions and electrons in turn strike more atoms, creating more positive ions in a chain reaction. The positive ions are all attracted to the negative
Anode ray
is sometimes a result of the sizes of the atoms in the alloy, because larger atoms exert a compressive force on neighboring atoms, and smaller atoms exert a tensile force on their neighbors, helping the alloy resist deformation. Sometimes alloys may exhibit marked differences in behavior even when small amounts of one element are present. For example, impurities in semiconducting ferromagnetic alloys lead to different properties, as first predicted by White, Hogan, Suhl, Tian Abrie and Nakamura. Some alloys are made by melting and mixing two or more metals. Bronze, an alloy of copper and tin, was the first alloy
Alloy
purity. This typically is the "nine-9" or 99.9999999% purity, nearly defect-free single crystalline material. Monocrystalline silicon of such purity is usually produced by the Czochralski process, is used to produce silicon wafers used in the semiconductor industry, in electronics, and in some high-cost and high-efficiency photovoltaic applications. Pure silicon is an intrinsic semiconductor, which means that unlike metals, it conducts electron holes and electrons released from atoms by heat; silicon's electrical conductivity increases with higher temperatures. Pure silicon has too low a conductivity (i.e., too high a resistivity) to be used as a circuit element in electronics. In practice, pure
Silicon
termed "shared pairs" or "bonding pairs", and the stable balance of attractive and repulsive forces between atoms, when they share electrons, is termed "covalent bonding". Ionic bonding is a type of chemical bond that involves the electrostatic attraction between oppositely charged ions, and is the primary interaction occurring in ionic compounds. The ions are atoms that have lost one or more electrons (termed cations) and atoms that have gained one or more electrons (termed anions). This transfer of electrons is termed "electrovalence" in contrast to covalence. In the simplest case, the cation is a metal atom and the anion is
Molecule
1972 Atlantic hurricane season The 1972 Atlantic hurricane season was a significantly below average season, having only four fully tropical named storms – the fewest since 1930. It officially began on June 1, 1972, and lasted until November 30, 1972. These dates conventionally delimit the period of each year when most tropical cyclones form in the Atlantic basin. The first storm, Subtropical Storm Alpha, developed on May 23 off the Southeast United States and struck Florida, causing minor damage and two fatalities. Although several other tropical depressions developed, only Tropical Depression Five is known to have affected land. The most
1972 Atlantic hurricane season
"who offered his place, his person, and his sword" to the Muslim leader in exchange for help in the civil war. Though Julian's "estates were ample, his followers bold and numerous", he "had little to hope and much to fear from the new reign." And he was too feeble to challenge Roderic directly. So he sought Musa's aid. For Musa, Julian, "by his Andalusian and Mauritanian commands, ... held in his hands the keys of the Spanish monarchy." And so Musa ordered some initial raids on the southern coast of the Iberian Peninsula in 710. In the spring of that
Muslim conquest of the Maghreb
Michael Oscislawski Michael Oscislawski (; born January 16, 1987 in Bytom) is a Polish-German footballer who plays for VfB Hüls. Oscislawski played in the youth first for TuS Kruckel and red and white Barop before he moved to Borussia Dortmund. Here he played until the end of the 2005/06 season, mainly in the junior teams, but was already in the 2004/05 season as a substitute for first jobs to the seniors, whom he played for the reserve of Borussia in the Regionalliga Nord. In the summer of 2006 he was finally firmly integrated into the squad of the second men's
Michael Oscislawski
Garcia Live Volume Ten Garcia Live Volume Ten is a two-CD live album by the Jerry Garcia Band. It contains the complete concert recorded on May 20, 1990 at the Hilo Civic Auditorium in Hilo, Hawaii. It was released on February 23, 2018. From February 1986 to November 1993, the lineup of the Jerry Garcia Band was Jerry Garcia (guitar, lead vocals), Melvin Seals (keyboards), John Kahn (bass), David Kemper (drums), Jaclyn LaBranch (backing vocals), and Gloria Jones (backing vocals). On AllMusic, Timothy Monger said, "... this May 20, 1990 show held at the Hilo Civic Auditorium was a benefit
Garcia Live Volume Ten
green and blue components and a separate sensor is then used for each colour. This complex camera technology is used in 3-chip cameras and allows for excellent colour reproduction at very high resolutions. Modern camera systems used in a document camera are able to provide high-resolution colour images at 30 frames per second. In a 3-chip camera, the measured resolution may be up to 1500 lines. In addition the image can be adapted to fit common display aspect ratios of 4:3, 16:9 and 16:10. Lighting is an essential part of a document camera. To ensure good colour rendition, the lighting
Document camera
presence of anthocyanins in the complexes with metals ions. Metalloanthocyanins are composed from anthocyanins, flavones and metal ions in the stochiometric amounts of 6:6:2, respectively. Typical metals in anthocyanin complexes are iron (Fe), Magnesium (Mg), aluminium (Al), copper (Cu), potassium (K) and tin (Sn). Anthocyanins that can form complexes with metal ions are only cyanidin or delphinidin type, because at least two free hydroxyl groups in the B-ring are necessary to be present Examples of metalloanthocyanins: Commelinin isolated from "Commelina communis" contains malonylawobanin (delphinidin type), flavocommelin (as a co-pigment) and magnesium ions in stochiometric ratio 6:6:2. Protocyanin is a blue
Basics of blue flower colouration
different. The cations most resistant to hydrolysis for their size and charge are hard pre-transition metal ions or lanthanide ions. The slightly less resistant group includes the transition metal ions. The third group contains mostly soft ions ion of post-transition metals. The ions which show the strongest tendency to hydrolyze for their charge and size are Pd, Sn and Hg. The standard enthalpy change for the first hydrolysis step is generally not very different from that of the dissociation of pure water. Consequently, the standard enthalpy change for the substitution reaction is close to zero. This is typical of reactions
Metal ions in aqueous solution
completely settled. In biochemistry, heavy metals are sometimes defined—on the basis of the Lewis acid (electronic pair acceptor) behaviour of their ions in aqueous solution—as class B and borderline metals. In this scheme, class A metal ions prefer oxygen donors; class B ions prefer nitrogen or sulfur donors; and borderline or ambivalent ions show either class A or B characteristics, depending on the circumstances. Class A metals, which tend to have low electronegativity and form bonds with large ionic character, are the alkali and alkaline earths, aluminium, the group 3 metals, and the lanthanides and actinides. Class B metals, which
Heavy metals
advanced models of metal properties consider the effect of the positive ions cores on the delocalised electrons. As most metals have crystalline structure, those ions are usually arranged into a periodic lattice. Mathematically, the potential of the ion cores can be treated by various models, the simplest being the nearly free electron model. Minerals are naturally occurring solids formed through various geological processes under high pressures. To be classified as a true mineral, a substance must have a crystal structure with uniform physical properties throughout. Minerals range in composition from pure elements and simple salts to very complex silicates with
Solid
availability of free ions of essential divalent cations like Fe and Zn showed that experiments with EGTA were better explained as having caused deficiencies in these essential ions. Classical demonstration of the requirements for trace metals requires careful cleaning of all glassware or plastic dishes and the use of very pure distilled water, and AR grade chemicals. By this method A.macrogynus and Achlya species were shown to require Fe, and Zn but not Ca. The traditional supply of calcium salts to fungal cultures may have met the need for trace elements as even A.R. calcium salts always contain other divalent
Allomyces macrogynus
atoms
Title: Metal. Content: face-centered cubic (fcc), and hexagonal close-packed (hcp). In bcc, each atom is positioned at the center of a cube of eight others. In fcc and hcp, each atom is surrounded by twelve others, but the stacking of the layers differs. Some metals adopt different structures depending on the temperature. The unit cell for each crystal structure is the smallest group of atoms which has the overall symmetry of the crystal, and from which the entire crystalline lattice can be built up by repetition in three dimensions. In the case of the body-centered cubic crystal structure shown above, the unit cell
atoms
atoms
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atoms
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atoms