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Ionization Energy of the Elements

Helium has the highest first ionization energy (24.587 eV) and caesium the lowest (3.894 eV).

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1 H 13.62 He 24.593 Li 5.394 Be 9.325 B 8.36 C 11.267 N 14.538 O 13.629 F 17.4210 Ne 21.5611 Na 5.1412 Mg 7.6513 Al 5.9914 Si 8.1515 P 10.4916 S 10.3617 Cl 12.9718 Ar 15.7619 K 4.3420 Ca 6.1121 Sc 6.5622 Ti 6.8323 V 6.7524 Cr 6.7725 Mn 7.4326 Fe 7.927 Co 7.8828 Ni 7.6429 Cu 7.7330 Zn 9.3931 Ga 632 Ge 7.933 As 9.7934 Se 9.7535 Br 11.8136 Kr 1437 Rb 4.1838 Sr 5.6939 Y 6.2240 Zr 6.6341 Nb 6.7642 Mo 7.0943 Tc 7.1244 Ru 7.3645 Rh 7.4646 Pd 8.3447 Ag 7.5848 Cd 8.9949 In 5.7950 Sn 7.3451 Sb 8.6152 Te 9.0153 I 10.4554 Xe 12.1355 Cs 3.8956 Ba 5.2157 La 5.5858 Ce 5.5459 Pr 5.4760 Nd 5.5261 Pm 5.5862 Sm 5.6463 Eu 5.6764 Gd 6.1565 Tb 5.8666 Dy 5.9467 Ho 6.0268 Er 6.1169 Tm 6.1870 Yb 6.2571 Lu 5.4372 Hf 6.8373 Ta 7.5574 W 7.8675 Re 7.8376 Os 8.4477 Ir 8.9778 Pt 8.9679 Au 9.2380 Hg 10.4481 Tl 6.1182 Pb 7.4283 Bi 7.2984 Po 8.4285 At 9.3286 Rn 10.7587 Fr 4.0788 Ra 5.2889 Ac 5.3890 Th 6.3191 Pa —92 U 6.1993 Np 6.2794 Pu 6.0395 Am 5.9796 Cm 5.9997 Bk 6.298 Cf 6.2899 Es 6.37100 Fm —101 Md —102 No 6.63103 Lr 4.96104 Rf —105 Db —106 Sg —107 Bh —108 Hs —109 Mt —110 Ds —111 Rg —112 Cn —113 Nh —114 Fl —115 Mc —116 Lv —117 Ts —118 Og —

Hydrogen

Nonmetals · Gas

Ionization energy 13.59843eV

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Ionization energy, eV 3.89391 24.58739 no data

Rises left to right across a period, peaking at the noble gases. Falls down a group. All values as a list ↓

All elements by ionization energy

Energy needed to remove the most loosely bound electron from an atom. The lower it is, the more easily the element gives up an electron, which is typical of metals.

Source: NIST Atomic Spectra Database

  1. 1 Helium 24.587eV
  2. 2 Neon 21.565eV
  3. 3 Fluorine 17.423eV
  4. 4 Argon 15.76eV
  5. 5 Nitrogen 14.534eV
  6. 6 Krypton 14eV
  7. 7 Oxygen 13.618eV
  8. 8 Hydrogen 13.598eV
  9. 9 Chlorine 12.968eV
  10. 10 Xenon 12.13eV
  11. 11 Bromine 11.814eV
  12. 12 Carbon 11.26eV
  13. 13 Radon 10.749eV
  14. 14 Phosphorus 10.487eV
  15. 15 Iodine 10.451eV
  16. 16 Mercury 10.438eV
  17. 17 Sulfur 10.36eV
  18. 18 Arsenic 9.789eV
  19. 19 Selenium 9.752eV
  20. 20 Zinc 9.394eV
  21. 21 Beryllium 9.323eV
  22. 22 Astatine 9.318eV
  23. 23 Gold 9.226eV
  24. 24 Tellurium 9.01eV
  25. 25 Cadmium 8.994eV
  26. 26 Iridium 8.967eV
  27. 27 Platinum 8.959eV
  28. 28 Antimony 8.608eV
  29. 29 Osmium 8.438eV
  30. 30 Polonium 8.418eV
  31. 31 Palladium 8.337eV
  32. 32 Boron 8.298eV
  33. 33 Silicon 8.152eV
  34. 34 Iron 7.902eV
  35. 35 Germanium 7.899eV
  36. 36 Cobalt 7.881eV
  37. 37 Tungsten 7.864eV
  38. 38 Rhenium 7.834eV
  39. 39 Copper 7.726eV
  40. 40 Magnesium 7.646eV
  41. 41 Nickel 7.64eV
  42. 42 Silver 7.576eV
  43. 43 Tantalum 7.55eV
  44. 44 Rhodium 7.459eV
  45. 45 Manganese 7.434eV
  46. 46 Lead 7.417eV
  47. 47 Ruthenium 7.361eV
  48. 48 Tin 7.344eV
  49. 49 Bismuth 7.286eV
  50. 50 Technetium 7.119eV
  51. 51 Molybdenum 7.092eV
  52. 52 Titanium 6.828eV
  53. 53 Hafnium 6.825eV
  54. 54 Chromium 6.767eV
  55. 55 Niobium 6.759eV
  56. 56 Vanadium 6.746eV
  57. 57 Zirconium 6.634eV
  58. 58 Nobelium 6.626eV
  59. 59 Scandium 6.561eV
  60. 60 Einsteinium 6.368eV
  61. 61 Thorium 6.307eV
  62. 62 Californium 6.282eV
  63. 63 Neptunium 6.266eV
  64. 64 Ytterbium 6.254eV
  65. 65 Yttrium 6.217eV
  66. 66 Berkelium 6.198eV
  67. 67 Uranium 6.194eV
  68. 68 Thulium 6.184eV
  69. 69 Gadolinium 6.15eV
  70. 70 Calcium 6.113eV
  71. 71 Thallium 6.108eV
  72. 72 Erbium 6.108eV
  73. 73 Plutonium 6.026eV
  74. 74 Holmium 6.022eV
  75. 75 Gallium 5.999eV
  76. 76 Curium 5.992eV
  77. 77 Aluminium 5.986eV
  78. 78 Americium 5.974eV
  79. 79 Dysprosium 5.939eV
  80. 80 Terbium 5.864eV
  81. 81 Indium 5.786eV
  82. 82 Strontium 5.695eV
  83. 83 Europium 5.67eV
  84. 84 Samarium 5.644eV
  85. 85 Promethium 5.582eV
  86. 86 Lanthanum 5.577eV
  87. 87 Cerium 5.539eV
  88. 88 Neodymium 5.525eV
  89. 89 Praseodymium 5.47eV
  90. 90 Lutetium 5.426eV
  91. 91 Lithium 5.392eV
  92. 92 Actinium 5.38eV
  93. 93 Radium 5.278eV
  94. 94 Barium 5.212eV
  95. 95 Sodium 5.139eV
  96. 96 Lawrencium 4.96eV
  97. 97 Potassium 4.341eV
  98. 98 Rubidium 4.177eV
  99. 99 Francium 4.073eV
  100. 100 Caesium 3.894eV

No data

Protactinium (Pa), Fermium (Fm), Mendelevium (Md), Rutherfordium (Rf), Dubnium (Db), Seaborgium (Sg), Bohrium (Bh), Hassium (Hs), Meitnerium (Mt), Darmstadtium (Ds), Roentgenium (Rg), Copernicium (Cn), Nihonium (Nh), Flerovium (Fl), Moscovium (Mc), Livermorium (Lv), Tennessine (Ts), Oganesson (Og)