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Atomic Mass of the Elements

Hydrogen is the lightest element (1.0080); of the elements with a standard atomic weight, uranium is the heaviest (238.03).

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1 H 1.00802 He 4.00263 Li 6.944 Be 9.01225 B 10.816 C 12.0117 N 14.0078 O 15.9999 F 18.99810 Ne 20.18011 Na 22.99012 Mg 24.30513 Al 26.98214 Si 28.08515 P 30.97416 S 32.0617 Cl 35.4518 Ar 39.9519 K 39.09820 Ca 40.07821 Sc 44.95622 Ti 47.86723 V 50.94224 Cr 51.99625 Mn 54.93826 Fe 55.84527 Co 58.93328 Ni 58.69329 Cu 63.54630 Zn 65.3831 Ga 69.72332 Ge 72.63033 As 74.92234 Se 78.97135 Br 79.90436 Kr 83.79837 Rb 85.46838 Sr 87.6239 Y 88.90640 Zr 91.22241 Nb 92.90642 Mo 95.9543 Tc [97]44 Ru 101.0745 Rh 102.9146 Pd 106.4247 Ag 107.8748 Cd 112.4149 In 114.8250 Sn 118.7151 Sb 121.7652 Te 127.6053 I 126.9054 Xe 131.2955 Cs 132.9156 Ba 137.3357 La 138.9158 Ce 140.1259 Pr 140.9160 Nd 144.2461 Pm [145]62 Sm 150.3663 Eu 151.9664 Gd 157.2565 Tb 158.9366 Dy 162.5067 Ho 164.9368 Er 167.2669 Tm 168.9370 Yb 173.0571 Lu 174.9772 Hf 178.4973 Ta 180.9574 W 183.8475 Re 186.2176 Os 190.2377 Ir 192.2278 Pt 195.0879 Au 196.9780 Hg 200.5981 Tl 204.3882 Pb 207.283 Bi 208.9884 Po [209]85 At [210]86 Rn [222]87 Fr [223]88 Ra [226]89 Ac [227]90 Th 232.0491 Pa 231.0492 U 238.0393 Np [237]94 Pu [244]95 Am [243]96 Cm [247]97 Bk [247]98 Cf [251]99 Es [252]100 Fm [257]101 Md [258]102 No [259]103 Lr [266]104 Rf [267]105 Db [268]106 Sg [269]107 Bh [270]108 Hs [269]109 Mt [278]110 Ds [281]111 Rg [282]112 Cn [285]113 Nh [286]114 Fl [289]115 Mc [290]116 Lv [293]117 Ts [294]118 Og [294]

Hydrogen

Nonmetals · Gas

Atomic mass 1.0080

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Atomic mass, u 1.008 294.211 no data

Grows with atomic number, with a few exceptions: argon is heavier than potassium, cobalt than nickel, tellurium than iodine, thorium than protactinium. All values as a list ↓

All elements by atomic mass

Average mass of an atom in unified atomic mass units (1 u is 1/12 of the mass of a carbon-12 atom). Accounts for the natural mix of the element’s isotopes.

Source: IUPAC CIAAW, PubChem (NIH)

  1. 1 Tennessine [294]
  2. 2 Oganesson [294]
  3. 3 Livermorium [293]
  4. 4 Moscovium [290]
  5. 5 Flerovium [289]
  6. 6 Nihonium [286]
  7. 7 Copernicium [285]
  8. 8 Roentgenium [282]
  9. 9 Darmstadtium [281]
  10. 10 Meitnerium [278]
  11. 11 Bohrium [270]
  12. 12 Hassium [269]
  13. 13 Seaborgium [269]
  14. 14 Dubnium [268]
  15. 15 Rutherfordium [267]
  16. 16 Lawrencium [266]
  17. 17 Nobelium [259]
  18. 18 Mendelevium [258]
  19. 19 Fermium [257]
  20. 20 Einsteinium [252]
  21. 21 Californium [251]
  22. 22 Curium [247]
  23. 23 Berkelium [247]
  24. 24 Plutonium [244]
  25. 25 Americium [243]
  26. 26 Uranium 238.03
  27. 27 Neptunium [237]
  28. 28 Thorium 232.04
  29. 29 Protactinium 231.04
  30. 30 Actinium [227]
  31. 31 Radium [226]
  32. 32 Francium [223]
  33. 33 Radon [222]
  34. 34 Astatine [210]
  35. 35 Polonium [209]
  36. 36 Bismuth 208.98
  37. 37 Lead 207.2
  38. 38 Thallium 204.38
  39. 39 Mercury 200.59
  40. 40 Gold 196.97
  41. 41 Platinum 195.08
  42. 42 Iridium 192.22
  43. 43 Osmium 190.23
  44. 44 Rhenium 186.21
  45. 45 Tungsten 183.84
  46. 46 Tantalum 180.95
  47. 47 Hafnium 178.49
  48. 48 Lutetium 174.97
  49. 49 Ytterbium 173.05
  50. 50 Thulium 168.93
  51. 51 Erbium 167.26
  52. 52 Holmium 164.93
  53. 53 Dysprosium 162.50
  54. 54 Terbium 158.93
  55. 55 Gadolinium 157.25
  56. 56 Europium 151.96
  57. 57 Samarium 150.36
  58. 58 Promethium [145]
  59. 59 Neodymium 144.24
  60. 60 Praseodymium 140.91
  61. 61 Cerium 140.12
  62. 62 Lanthanum 138.91
  63. 63 Barium 137.33
  64. 64 Caesium 132.91
  65. 65 Xenon 131.29
  66. 66 Tellurium 127.60
  67. 67 Iodine 126.90
  68. 68 Antimony 121.76
  69. 69 Tin 118.71
  70. 70 Indium 114.82
  71. 71 Cadmium 112.41
  72. 72 Silver 107.87
  73. 73 Palladium 106.42
  74. 74 Rhodium 102.91
  75. 75 Ruthenium 101.07
  76. 76 Technetium [97]
  77. 77 Molybdenum 95.95
  78. 78 Niobium 92.906
  79. 79 Zirconium 91.222
  80. 80 Yttrium 88.906
  81. 81 Strontium 87.62
  82. 82 Rubidium 85.468
  83. 83 Krypton 83.798
  84. 84 Bromine 79.904
  85. 85 Selenium 78.971
  86. 86 Arsenic 74.922
  87. 87 Germanium 72.630
  88. 88 Gallium 69.723
  89. 89 Zinc 65.38
  90. 90 Copper 63.546
  91. 91 Cobalt 58.933
  92. 92 Nickel 58.693
  93. 93 Iron 55.845
  94. 94 Manganese 54.938
  95. 95 Chromium 51.996
  96. 96 Vanadium 50.942
  97. 97 Titanium 47.867
  98. 98 Scandium 44.956
  99. 99 Calcium 40.078
  100. 100 Argon 39.95
  101. 101 Potassium 39.098
  102. 102 Chlorine 35.45
  103. 103 Sulfur 32.06
  104. 104 Phosphorus 30.974
  105. 105 Silicon 28.085
  106. 106 Aluminium 26.982
  107. 107 Magnesium 24.305
  108. 108 Sodium 22.990
  109. 109 Neon 20.180
  110. 110 Fluorine 18.998
  111. 111 Oxygen 15.999
  112. 112 Nitrogen 14.007
  113. 113 Carbon 12.011
  114. 114 Boron 10.81
  115. 115 Beryllium 9.0122
  116. 116 Lithium 6.94
  117. 117 Helium 4.0026
  118. 118 Hydrogen 1.0080

[ ] — mass number of the most stable isotope