Periodic table chart
Ionisation energy chart
First ionisation energy is the energy needed to remove the most loosely held electron from a neutral atom in the gas phase. Values are in electronvolts (eV); the table also gives them in kJ/mol.
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- 1H13.6
- 2He24.59
- 3Li5.39
- 4Be9.32
- 5B8.3
- 6C11.26
- 7N14.53
- 8O13.62
- 9F17.42
- 10Ne21.57
- 11Na5.14
- 12Mg7.65
- 13Al5.99
- 14Si8.15
- 15P10.49
- 16S10.36
- 17Cl12.97
- 18Ar15.76
- 19K4.34
- 20Ca6.11
- 21Sc6.56
- 22Ti6.83
- 23V6.75
- 24Cr6.77
- 25Mn7.43
- 26Fe7.9
- 27Co7.88
- 28Ni7.64
- 29Cu7.73
- 30Zn9.39
- 31Ga6
- 32Ge7.9
- 33As9.82
- 34Se9.75
- 35Br11.81
- 36Kr14
- 37Rb4.18
- 38Sr5.7
- 39Y6.22
- 40Zr6.63
- 41Nb6.76
- 42Mo7.09
- 43Tc7.28
- 44Ru7.36
- 45Rh7.46
- 46Pd8.34
- 47Ag7.58
- 48Cd8.99
- 49In5.79
- 50Sn7.34
- 51Sb8.64
- 52Te9.01
- 53I10.45
- 54Xe12.13
- 55Cs3.89
- 56Ba5.21
- 57La5.58
- 58Ce5.54
- 59Pr5.46
- 60Nd5.53
- 61Pm5.55
- 62Sm5.64
- 63Eu5.67
- 64Gd6.15
- 65Tb5.86
- 66Dy5.94
- 67Ho6.02
- 68Er6.11
- 69Tm6.18
- 70Yb6.25
- 71Lu5.43
- 72Hf6.83
- 73Ta7.89
- 74W7.98
- 75Re7.88
- 76Os8.7
- 77Ir9.1
- 78Pt9
- 79Au9.23
- 80Hg10.44
- 81Tl6.11
- 82Pb7.42
- 83Bi7.29
- 84Po8.42
- 85At9.5
- 86Rn10.75
- 87Fr3.9
- 88Ra5.28
- 89Ac5.17
- 90Th6.08
- 91Pa5.89
- 92U6.19
- 93Np6.27
- 94Pu6.06
- 95Am5.99
- 96Cm6.02
- 97Bk6.23
- 98Cf6.3
- 99Es6.42
- 100Fm6.5
- 101Md6.58
- 102No6.65
- 103Lr—
- 104Rf—
- 105Db—
- 106Sg—
- 107Bh—
- 108Hs—
- 109Mt—
- 110Ds—
- 111Rg—
- 112Cn—
- 113Nh—
- 114Fl—
- 115Mc—
- 116Lv—
- 117Ts—
- 118Og—
LowHigh(eV)
No dataThe trend
Ionisation energy rises across a period as the nuclear charge grows, and falls down a group as the outer electron sits farther from the nucleus. Helium has the highest value of all and the alkali metals the lowest, which is why they lose an electron so easily. Two small dips break the pattern in each period: at group 13 (boron is lower than beryllium) and at group 16 (oxygen is lower than nitrogen).
Highest
- Helium (He)24.59 eV
- Neon (Ne)21.57 eV
- Fluorine (F)17.42 eV
- Argon (Ar)15.76 eV
- Nitrogen (N)14.53 eV
Lowest
- Caesium (Cs)3.89 eV
- Francium (Fr)3.9 eV
- Rubidium (Rb)4.18 eV
- Potassium (K)4.34 eV
- Sodium (Na)5.14 eV
1st ionisation energy of every element
| No. | Element | 1st ionisation energy (eV) | kJ/mol |
|---|---|---|---|
| 1 | Hydrogen (H) | 13.6 | 1,312 |
| 2 | Helium (He) | 24.59 | 2,372.3 |
| 3 | Lithium (Li) | 5.39 | 520.2 |
| 4 | Beryllium (Be) | 9.32 | 899.5 |
| 5 | Boron (B) | 8.3 | 800.6 |
| 6 | Carbon (C) | 11.26 | 1,086.5 |
| 7 | Nitrogen (N) | 14.53 | 1,402.3 |
| 8 | Oxygen (O) | 13.62 | 1,313.9 |
| 9 | Fluorine (F) | 17.42 | 1,681 |
| 10 | Neon (Ne) | 21.57 | 2,080.7 |
| 11 | Sodium (Na) | 5.14 | 495.8 |
| 12 | Magnesium (Mg) | 7.65 | 737.7 |
| 13 | Aluminium (Al) | 5.99 | 577.5 |
| 14 | Silicon (Si) | 8.15 | 786.5 |
| 15 | Phosphorus (P) | 10.49 | 1,011.8 |
| 16 | Sulfur (S) | 10.36 | 999.6 |
| 17 | Chlorine (Cl) | 12.97 | 1,251.2 |
| 18 | Argon (Ar) | 15.76 | 1,520.6 |
| 19 | Potassium (K) | 4.34 | 418.8 |
| 20 | Calcium (Ca) | 6.11 | 589.8 |
| 21 | Scandium (Sc) | 6.56 | 633.1 |
| 22 | Titanium (Ti) | 6.83 | 658.8 |
| 23 | Vanadium (V) | 6.75 | 650.9 |
| 24 | Chromium (Cr) | 6.77 | 652.9 |
| 25 | Manganese (Mn) | 7.43 | 717.3 |
| 26 | Iron (Fe) | 7.9 | 762.5 |
| 27 | Cobalt (Co) | 7.88 | 760.4 |
| 28 | Nickel (Ni) | 7.64 | 737.1 |
| 29 | Copper (Cu) | 7.73 | 745.5 |
| 30 | Zinc (Zn) | 9.39 | 906.4 |
| 31 | Gallium (Ga) | 6 | 578.8 |
| 32 | Germanium (Ge) | 7.9 | 762 |
| 33 | Arsenic (As) | 9.82 | 947 |
| 34 | Selenium (Se) | 9.75 | 941 |
| 35 | Bromine (Br) | 11.81 | 1,139.9 |
| 36 | Krypton (Kr) | 14 | 1,350.8 |
| 37 | Rubidium (Rb) | 4.18 | 403 |
| 38 | Strontium (Sr) | 5.7 | 549.5 |
| 39 | Yttrium (Y) | 6.22 | 600 |
| 40 | Zirconium (Zr) | 6.63 | 640.1 |
| 41 | Niobium (Nb) | 6.76 | 652.1 |
| 42 | Molybdenum (Mo) | 7.09 | 684.3 |
| 43 | Technetium (Tc) | 7.28 | 702 |
| 44 | Ruthenium (Ru) | 7.36 | 710.2 |
| 45 | Rhodium (Rh) | 7.46 | 719.7 |
| 46 | Palladium (Pd) | 8.34 | 804.4 |
| 47 | Silver (Ag) | 7.58 | 731 |
| 48 | Cadmium (Cd) | 8.99 | 867.8 |
| 49 | Indium (In) | 5.79 | 558.3 |
| 50 | Tin (Sn) | 7.34 | 708.6 |
| 51 | Antimony (Sb) | 8.64 | 834 |
| 52 | Tellurium (Te) | 9.01 | 869.3 |
| 53 | Iodine (I) | 10.45 | 1,008.4 |
| 54 | Xenon (Xe) | 12.13 | 1,170.4 |
| 55 | Caesium (Cs) | 3.89 | 375.7 |
| 56 | Barium (Ba) | 5.21 | 502.9 |
| 57 | Lanthanum (La) | 5.58 | 538.1 |
| 58 | Cerium (Ce) | 5.54 | 534.4 |
| 59 | Praseodymium (Pr) | 5.46 | 527 |
| 60 | Neodymium (Nd) | 5.53 | 533.1 |
| 61 | Promethium (Pm) | 5.55 | 540 |
| 62 | Samarium (Sm) | 5.64 | 544.5 |
| 63 | Europium (Eu) | 5.67 | 547.1 |
| 64 | Gadolinium (Gd) | 6.15 | 593.4 |
| 65 | Terbium (Tb) | 5.86 | 565.8 |
| 66 | Dysprosium (Dy) | 5.94 | 573 |
| 67 | Holmium (Ho) | 6.02 | 581 |
| 68 | Erbium (Er) | 6.11 | 589.3 |
| 69 | Thulium (Tm) | 6.18 | 596.7 |
| 70 | Ytterbium (Yb) | 6.25 | 603.4 |
| 71 | Lutetium (Lu) | 5.43 | 523.5 |
| 72 | Hafnium (Hf) | 6.83 | 658.5 |
| 73 | Tantalum (Ta) | 7.89 | 761 |
| 74 | Tungsten (W) | 7.98 | 770 |
| 75 | Rhenium (Re) | 7.88 | 760 |
| 76 | Osmium (Os) | 8.7 | 840 |
| 77 | Iridium (Ir) | 9.1 | 880 |
| 78 | Platinum (Pt) | 9 | 870 |
| 79 | Gold (Au) | 9.23 | 890.1 |
| 80 | Mercury (Hg) | 10.44 | 1,007.1 |
| 81 | Thallium (Tl) | 6.11 | 589.4 |
| 82 | Lead (Pb) | 7.42 | 715.6 |
| 83 | Bismuth (Bi) | 7.29 | 703 |
| 84 | Polonium (Po) | 8.42 | 812.1 |
| 85 | Astatine (At) | 9.5 | 899 |
| 86 | Radon (Rn) | 10.75 | 1,037 |
| 87 | Francium (Fr) | 3.9 | 380 |
| 88 | Radium (Ra) | 5.28 | 509.3 |
| 89 | Actinium (Ac) | 5.17 | 499 |
| 90 | Thorium (Th) | 6.08 | 587 |
| 91 | Protactinium (Pa) | 5.89 | 568 |
| 92 | Uranium (U) | 6.19 | 597.6 |
| 93 | Neptunium (Np) | 6.27 | 604.5 |
| 94 | Plutonium (Pu) | 6.06 | 584.7 |
| 95 | Americium (Am) | 5.99 | 578 |
| 96 | Curium (Cm) | 6.02 | 581 |
| 97 | Berkelium (Bk) | 6.23 | 601 |
| 98 | Californium (Cf) | 6.3 | 608 |
| 99 | Einsteinium (Es) | 6.42 | 619 |
| 100 | Fermium (Fm) | 6.5 | 627 |
| 101 | Mendelevium (Md) | 6.58 | 635 |
| 102 | Nobelium (No) | 6.65 | 642 |
| 103 | Lawrencium (Lr) | — | 470 |
| 104 | Rutherfordium (Rf) | — | 580 |
| 105 | Dubnium (Db) | — | — |
| 106 | Seaborgium (Sg) | — | — |
| 107 | Bohrium (Bh) | — | — |
| 108 | Hassium (Hs) | — | — |
| 109 | Meitnerium (Mt) | — | — |
| 110 | Darmstadtium (Ds) | — | — |
| 111 | Roentgenium (Rg) | — | — |
| 112 | Copernicium (Cn) | — | — |
| 113 | Nihonium (Nh) | — | — |
| 114 | Flerovium (Fl) | — | — |
| 115 | Moscovium (Mc) | — | — |
| 116 | Livermorium (Lv) | — | — |
| 117 | Tennessine (Ts) | — | — |
| 118 | Oganesson (Og) | — | — |