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Atomic Symbol Name Weight

1

1 H Hydrogen 1.008

2 He Helium 4.0026

2

3 Li Lithium 6.94

4 Be Beryllium 9.0122

5 B Boron 10.81

6 C Carbon 12.011

7 N Nitrogen 14.007

8 O Oxygen 15.999

9 F Fluorine 18.998

10 Ne Neon 20.180

3

11 Na Sodium 22.990

12 Mg Magnesium 24.305

13 Al Aluminium 26.982

14 Si Silicon 28.085

15 P Phosphorus 30.974

16 S Sulfur 32.06

17 Cl Chlorine 35.45

18 Ar Argon 39.948

4

19 K Potassium 39.098

20 Ca Calcium 40.078

21 Sc Scandium 44.956

22 Ti Titanium 47.867

23 V Vanadium 50.942

24 Cr Chromium 51.996

25 Mn Manganese 54.938

26 Fe Iron 55.845

27 Co Cobalt 58.933

28 Ni Nickel 58.693

29 Cu Copper 63.546

30 Zn Zinc 65.38

31 Ga Gallium 69.723

32 Ge Germanium 72.630

33 As Arsenic 74.922

34 Se Selenium 78.971

35 Br Bromine 79.904

36 Kr Krypton 83.798

5

37 Rb Rubidium 85.468

38 Sr Strontium 87.62

39 Y Yttrium 88.906

40 Zr Zirconium 91.224

41 Nb Niobium 92.906

42 Mo Molybdenum 95.95

43 Tc Technetium (98)

44 Ru Ruthenium 101.07

45 Rh Rhodium 102.91

46 Pd Palladium 106.42

47 Ag Silver 107.87

48 Cd Cadmium 112.41

49 In Indium 114.82

50 Sn Tin 118.71

51 Sb Antimony 121.76

52 Te Tellurium 127.60

53 I Iodine 126.90

54 Xe Xenon 131.29

6

55 Cs Caesium 132.91

56 Ba Barium 137.33

57–71

6

57 La Lanthanum 138.91

58 Ce Cerium 140.12

59 Pr Praseodymium 140.91

60 Nd Neodymium 144.24

61 Pm Promethium (145)

62 Sm Samarium 150.36

63 Eu Europium 151.96

64 Gd Gadolinium 157.25

65 Tb Terbium 158.93

66 Dy Dysprosium 162.50

67 Ho Holmium 164.93

68 Er Erbium 167.26

69 Tm Thulium 168.93

70 Yb Ytterbium 173.05

71 Lu Lutetium 174.97

72 Hf Hafnium 178.49

73 Ta Tantalum 180.95

74 W Tungsten 183.84

75 Re Rhenium 186.21

76 Os Osmium 190.23

77 Ir Iridium 192.22

78 Pt Platinum 195.08

79 Au Gold 196.97

80 Hg Mercury 200.59

81 Tl Thallium 204.38

82 Pb Lead 207.2

83 Bi Bismuth 208.98

84 Po Polonium (209)

85 At Astatine (210)

86 Rn Radon (222)

7

87 Fr Francium (223)

88 Ra Radium (226)

89–103

7

89 Ac Actinium (227)

90 Th Thorium 232.04

91 Pa Protactinium 231.04

92 U Uranium 238.03

93 Np Neptunium (237)

94 Pu Plutonium (244)

95 Am Americium (243)

96 Cm Curium (247)

97 Bk Berkelium (247)

98 Cf Californium (251)

99 Es Einsteinium (252)

100 Fm Fermium (257)

101 Md Mendelevium (258)

102 No Nobelium (259)

103 Lr Lawrencium (266)

104 Rf Rutherfordium (267)

105 Db Dubnium (268)

106 Sg Seaborgium (269)

107 Bh Bohrium (270)

108 Hs Hassium (277)

109 Mt Meitnerium (278)

110 Ds Darmstadtium (281)

111 Rg Roentgenium (282)

112 Cn Copernicium (285)

113 Nh Nihonium (286)

114 Fl Flerovium (289)

115 Mc Moscovium (290)

116 Lv Livermorium (293)

117 Ts Tennessine (294)

118 Og Oganesson (294)

For elements with no stable isotopes, the mass number of the isotope with the longest half-life is in parentheses.