A<unk>  is an abbreviation or short representation of the name of a<unk>  element, generally assigned in relation to its Latin name. Natural elements all have<unk> s of one or two letters; some man-made elements have temporary<unk> s of three letters.<unk> s are listed in the periodic table and are used as shorthand and in<unk>  equations, e.g.,
Because<unk> s are often derived from the Latin or Greek name of the element, they may not bear much similarity to the common Englis name, e.g., Na for sodium (Latin natrium) and Au for gold (Latin aurum).
In China, each<unk>  element is assigned an ideograph as its<unk> ; most of them have been explicitly created for this purpose.<unk> s may also be changed to show if one particular isotope of an atom that is specified, as well as to show other attributes such as ionization and oxidation state of a<unk>  compound.
Examples of families
Alkali Metals
Alkaline Earth Metals
Transition Metals
Halogen Gases
Inert Gases (Noble Gases)
Examples of physical properties
Density
Boiling Point 212 degrees F
Melting Point
Conductivity
Heat Capacity
Examples of<unk>  properties:
Valence
Reactivity
Radioactivity
For complete listings of the<unk>  elements and their<unk> s, see:
List of elements by<unk> 
List of elements by name
List of elements by number
Periodic table of the elements
Chemical symbol
Potential energy
Free energy
Peptide sequence
Idose
Subscript
Isomer
Molecular orbital