Electron affinity of the elements

Electron affinity is the energy released when a neutral atom in the gas phase takes on one extra electron. The larger the number, the more stable the negative ion; values are in electronvolts, with kJ/mol alongside in the ranked list. The values are PubChem’s, published by the US National Institutes of Health, except fluorine’s, germanium’s, rubidium’s, indium’s, tin’s, thallium’s and astatine’s, which the caveats explain. It gives one for 57 of the 118 elements; the rest are hatched in the table below rather than coloured as if they were zero.

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H 0.754, hydrogen He no value, helium Li 0.618, lithium Be no value, beryllium B 0.277, boron C 1.26, carbon N no value, nitrogen O 1.46, oxygen F 3.4, fluorine Ne no value, neon Na 0.548, sodium Mg no value, magnesium Al 0.441, aluminium Si 1.39, silicon P 0.746, phosphorus S 2.08, sulfur Cl 3.62, chlorine Ar no value, argon K 0.501, potassium Ca no value, calcium Sc 0.188, scandium Ti 0.079, titanium V 0.525, vanadium Cr 0.666, chromium Mn no value, manganese Fe 0.163, iron Co 0.661, cobalt Ni 1.16, nickel Cu 1.23, copper Zn no value, zinc Ga 0.3, gallium Ge 1.23, germanium As 0.81, arsenic Se 2.02, selenium Br 3.37, bromine Kr no value, krypton Rb 0.486, rubidium Sr no value, strontium Y 0.307, yttrium Zr 0.426, zirconium Nb 0.893, niobium Mo 0.746, molybdenum Tc 0.55, technetium Ru 1.05, ruthenium Rh 1.14, rhodium Pd 0.557, palladium Ag 1.3, silver Cd no value, cadmium In 0.384, indium Sn 1.11, tin Sb 1.07, antimony Te 1.97, tellurium I 3.06, iodine Xe no value, xenon Cs 0.472, caesium Ba no value, barium La 0.5, lanthanum Ce 0.5, cerium Pr no value, praseodymium Nd no value, neodymium Pm no value, promethium Sm no value, samarium Eu no value, europium Gd no value, gadolinium Tb no value, terbium Dy no value, dysprosium Ho no value, holmium Er no value, erbium Tm no value, thulium Yb no value, ytterbium Lu no value, lutetium Hf no value, hafnium Ta 0.322, tantalum W 0.815, tungsten Re 0.15, rhenium Os 1.1, osmium Ir 1.57, iridium Pt 2.13, platinum Au 2.31, gold Hg no value, mercury Tl 0.32, thallium Pb 0.36, lead Bi 0.946, bismuth Po 1.9, polonium At 2.42, astatine Rn no value, radon Fr 0.47, francium Ra no value, radium Ac no value, actinium Th no value, thorium Pa no value, protactinium U no value, uranium Np no value, neptunium Pu no value, plutonium Am no value, americium Cm no value, curium Bk no value, berkelium Cf no value, californium Es no value, einsteinium Fm no value, fermium Md no value, mendelevium No no value, nobelium Lr no value, lawrencium Rf no value, rutherfordium Db no value, dubnium Sg no value, seaborgium Bh no value, bohrium Hs no value, hassium Mt no value, meitnerium Ds no value, darmstadtium Rg no value, roentgenium Cn no value, copernicium Nh no value, nihonium Fl no value, flerovium Mc no value, moscovium Lv no value, livermorium Ts no value, tennessine Og no value, oganesson

How it changes across a period and down a group

Across a period electron affinity broadly rises towards the halogens, which complete a p subshell by taking one electron and release the most energy doing so. Chlorine has the highest value in the table, at 3.617 eV.

Down a group it does not simply fall, and the second period is the main reason. Fluorine’s affinity, 3.40119 eV, is below chlorine’s, and oxygen’s, 1.461 eV, is below sulfur’s, 2.077 eV, because an electron added to their small, crowded 2p shell is repelled by the electrons already there.

Below period 3 the values drift down again, bromine at 3.365 eV and iodine at 3.059 eV both sitting below chlorine.

Gold and platinum stand out among the metals, at 2.309 and 2.128 eV, higher than sulfur. It is a relativistic effect on their outer s orbital, and gold is stable enough as a negative ion to form compounds such as caesium auride.

Extremes and exceptions

Highest and lowest

• Chlorine, 3.617 eV
• Fluorine, 3.40119 eV
• Bromine, 3.365 eV
• Titanium, 0.079 eV
• Rhenium, 0.15 eV
• Iron, 0.163 eV

The three highest and the three lowest values in the table.

Higher in period 3 than in period 2

• Boron to aluminium: 0.277 to 0.441 eV
• Carbon to silicon: 1.263 to 1.385 eV
• Oxygen to sulfur: 1.461 to 2.077 eV
• Fluorine to chlorine: 3.40119 to 3.617 eV

In each of these groups the second-period element gains an electron less readily than the one below it, because its compact 2p shell leaves the new electron closer to the ones already there.

The 57 elements with a value, ranked

Equal values share a rank, marked with =.

No value in PubChem’s table, so not ranked: helium, beryllium, nitrogen, neon, magnesium, argon, calcium, manganese, zinc, krypton, strontium, cadmium, xenon, barium, praseodymium, neodymium, promethium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, lutetium, hafnium, mercury, radon, radium, actinium, thorium, protactinium, uranium, neptunium, plutonium, americium, curium, berkelium, californium, einsteinium, fermium, mendelevium, nobelium, lawrencium, rutherfordium, dubnium, seaborgium, bohrium, hassium, meitnerium, darmstadtium, roentgenium, copernicium, nihonium, flerovium, moscovium, livermorium, tennessine and oganesson.

The values are facts and free to use; this table’s selection and presentation are © 2026 ScienceQuest.

Caveats

• A blank is not zero. PubChem’s table gives a value for 57 of the 118 elements. For elements such as helium, beryllium, nitrogen, magnesium, zinc and mercury, whose negative ions are not stable, PubChem’s own element records quote two figures: 0 eV from a 1990 paper, and a small estimate from a 1969 one that is positive for some of them and negative for others. The table this page is built from gives neither, and nor does this page.
• Neon, argon, krypton, xenon and radon are blank as well, and none of them forms a stable negative ion either. Of the remaining gaps, 28 are in the f-block, 15 come after element 103, and calcium, manganese, strontium, cadmium, barium, hafnium and radium are missing too; none of those is a statement that the value is zero.
• PubChem lists affinities as positive numbers, the energy released when the ion forms. Some books use the opposite sign convention, the energy change of the reaction, so check which one before comparing.
• Fluorine’s 3.40119 eV is its measured electron affinity, from Wikipedia’s electron affinity data page, in place of PubChem’s 3.339 eV, which would put it below bromine rather than second only to chlorine.
• Germanium’s 1.2327 eV, rubidium’s 0.48592 eV, indium’s 0.38392 eV and tin’s 1.11207 eV are their measured electron affinities, from the same data page, in place of PubChem’s 1.35, 0.468, 0.3 and 1.2 eV.
• Thallium’s 0.320053 eV and astatine’s 2.41578 eV are their measured electron affinities, from the same data page, in place of PubChem’s 0.2 and 2.8 eV, older figures that those measurements replaced.

See also

• The interactive periodic table, with every element’s details
• First ionisation energy, the energy to remove an electron instead
• All the elements, each with its own page of data