Editing Electron affinity (section)

== Electron affinities of the elements ==
[[File:Electron affinity of the elements.svg|thumb|200px|Electron affinity (''E''<sub>ea</sub>) vs atomic number (''Z''). Note the sign convention explanation in the previous section.]]
{{Main|Electron affinity (data page)}}
Although ''E''<sub>ea</sub> varies greatly across the [[periodic table]], some patterns emerge. Generally, [[nonmetals]] have more positive ''E''<sub>ea</sub> than [[metal]]s. Atoms whose anions are more stable than neutral atoms have a greater ''E''<sub>ea</sub>. [[Chlorine]] most strongly attracts extra electrons; [[neon]] most weakly attracts an extra electron. The electron affinities of the noble gases have not been conclusively measured, so they may or may not have slightly negative values.

''E''<sub>ea</sub> generally increases across a period (row) in the periodic table prior to reaching group 18. This is caused by the filling of the valence shell of the atom; a [[halogen|group 17]] atom releases more energy than a [[Group 1 element|group 1]] atom on gaining an electron because it obtains a filled [[electron shell|valence shell]] and therefore is more stable. In group 18, the valence shell is full, meaning that added electrons are unstable, tending to be ejected very quickly.

Counterintuitively,  ''E''<sub>ea</sub> does ''not'' decrease when progressing down most columns of the periodic table. For example, ''E''<sub>ea</sub> actually increases consistently on descending the column for the [[Group 2 element|group 2]] data. Thus, electron affinity follows the same "left-right" trend as electronegativity, but not the "up-down" trend.

The following data are quoted in [[Joule per mole|kJ/mol]].

{| class="mw-collapsible {{#if:{{{state|collapsed}}}|collapsed|mw-collapsed}}" style="text-align: center; background: {{Element color|table background}}; border: 1px solid {{Element color|table border}}; width: 100%; max-width: 1300px; margin: 0 auto; padding: 2px; cellpadding: 0; cellspacing: 1;"
|+ style="background: {{Element color|table title}}; padding: 2px 4px;" | [[Electron affinities]] in the [[periodic table]]
|- style="background: {{Element color|table colheader}}"
! width="1.0%" | <small>[[Periodic table group|Group]]&nbsp;→</small>
! width="5.4%" | [[Alkali metal|1]]
! width="5.4%" | [[Alkaline earth metal|2]]
! width="1.8%" | 
! width="5.4%" | [[Group 3 element|3]]
! width="5.4%" | [[Group 4 element|4]]
! width="5.4%" | [[Group 5 element|5]]
! width="5.4%" | [[Group 6 element|6]]
! width="5.4%" | [[Group 7 element|7]]
! width="5.4%" | [[Group 8 element|8]]
! width="5.4%" | [[Group 9 element|9]]
! width="5.4%" | [[Group 10 element|10]]
! width="5.4%" | [[Group 11 element|11]]
! width="5.4%" | [[Group 12 element|12]]
! width="5.4%" | [[Boron group|13]]
! width="5.4%" | [[Carbon group|14]]
! width="5.4%" | [[Pnictogen|15]]
! width="5.4%" | [[Chalcogen|16]]
! width="5.4%" | [[Halogen|17]]
! width="5.4%" | [[Noble gas|18]]
|-
! <small>↓&nbsp;[[Periodic table period|Period]]</small>
| colspan="20"|<br />
|-
! [[Period 1 element|1]]
| {{element cell property|H |hydrogen  |73 |s-block|Primordial}}
| colspan="17"|<br />
| {{element cell property|He|helium    |(−50) |s-block|Primordial}}
|-
! [[Period 2 element|2]]
| {{element cell property|Li|lithium   |60 |s-block|Primordial}}
| {{element cell property|Be|beryllium |(−50)|s-block|Primordial}}
| colspan="11"|<br />
| {{element cell property|B |boron     |27 |p-block|Primordial}}
| {{element cell property|C |carbon    |122 |p-block|Primordial}}
| {{element cell property|N |nitrogen  |−7 |p-block|Primordial}}
| {{element cell property|O |oxygen    |141 |p-block|Primordial}}
| {{element cell property|F |fluorine  |328 |p-block|Primordial}}
| {{element cell property|Ne|neon      |(−120) |p-block|Primordial}}
|-
! [[Period 3 element|3]]
| {{element cell property|Na|sodium    |53 |s-block|Primordial}}
| {{element cell property|Mg|magnesium |(−40) |s-block|Primordial}}
| colspan="11"|<br />
| {{element cell property|Al|aluminium |42 |p-block|Primordial}}
| {{element cell property|Si|silicon   |134 |p-block|Primordial}}
| {{element cell property|P |phosphorus|72 |p-block|Primordial}}
| {{element cell property|S |sulfur    |200 |p-block|Primordial}}
| {{element cell property|Cl|chlorine  |349 |p-block|Primordial}}
| {{element cell property|Ar|argon     |(−96) |p-block|Primordial}}
|-
! [[Period 4 element|4]]
| {{element cell property|K |potassium |48 |s-block|Primordial}}
| {{element cell property|Ca|calcium   |2 |s-block|Primordial}}
|
| {{element cell property|Sc|scandium  |18|d-block|Primordial}}
| {{element cell property|Ti|titanium  |7 |d-block|Primordial}}
| {{element cell property|V |vanadium  |51 |d-block|Primordial}}
| {{element cell property|Cr|chromium  |65 |d-block|Primordial}}
| {{element cell property|Mn|manganese |(−50) |d-block|Primordial}}
| {{element cell property|Fe|iron      |15 |d-block|Primordial}}
| {{element cell property|Co|cobalt    |64 |d-block|Primordial}}
| {{element cell property|Ni|nickel    |112 |d-block|Primordial}}
| {{element cell property|Cu|copper    |119 |d-block|Primordial}}
| {{element cell property|Zn|zinc      |(−60) |d-block|Primordial}}
| {{element cell property|Ga|gallium   |29 |p-block|Primordial}}
| {{element cell property|Ge|germanium |119 |p-block|Primordial}}
| {{element cell property|As|arsenic   |78 |p-block|Primordial}}
| {{element cell property|Se|selenium  |195 |p-block|Primordial}}
| {{element cell property|Br|bromine   |325 |p-block|Primordial}}
| {{element cell property|Kr|krypton   |(−96) |p-block|Primordial}}
|-
! [[Period 5 element|5]]
| {{element cell property|Rb|rubidium  |47 |s-block|Primordial}}
| {{element cell property|Sr|strontium |5 |s-block|Primordial}}
|
| {{element cell property|Y |yttrium   |30 |d-block|Primordial}}
| {{element cell property|Zr|zirconium |42 |d-block|Primordial}}
| {{element cell property|Nb|niobium   |89 |d-block|Primordial}}
| {{element cell property|Mo|molybdenum|72 |d-block|Primordial}}
| {{element cell property|Tc|technetium|(53)  |d-block|from decay}}
| {{element cell property|Ru|ruthenium |(101)|d-block|Primordial}}
| {{element cell property|Rh|rhodium   |110|d-block|Primordial}}
| {{element cell property|Pd|palladium |54|d-block|Primordial}}
| {{element cell property|Ag|silver    |126|d-block|Primordial}}
| {{element cell property|Cd|cadmium   |(−70)|d-block|Primordial}}
| {{element cell property|In|indium    |37|p-block|Primordial}}
| {{element cell property|Sn|tin       |107|p-block|Primordial}}
| {{element cell property|Sb|antimony  |101|p-block|Primordial}}
| {{element cell property|Te|tellurium |190|p-block|Primordial}}
| {{element cell property|I |iodine    |295|p-block|Primordial}}
| {{element cell property|Xe|xenon     |(−80)|p-block|Primordial}}
|-
! [[Period 6 element|6]]
| {{element cell property|Cs|caesium   |46|s-block|Primordial}}
| {{element cell property|Ba|barium    |14|s-block|Primordial}}
| {{element cell-asterisk|1}}
| {{element cell property|Lu|lutetium  |23|d-block|Primordial}}
| {{element cell property|Hf|hafnium   |17|d-block|Primordial}}
| {{element cell property|Ta|tantalum  |31|d-block|Primordial}}
| {{element cell property|W |tungsten  |79|d-block|Primordial}}
| {{element cell property|Re|rhenium   |6|d-block|Primordial}}
| {{element cell property|Os|osmium    |104|d-block|Primordial}}
| {{element cell property|Ir|iridium   |151|d-block|Primordial}}
| {{element cell property|Pt|platinum  |205|d-block|Primordial}}
| {{element cell property|Au|gold      |223|d-block|Primordial}}
| {{element cell property|Hg|mercury   |(−50)|d-block|Primordial|mercury (element)}}
| {{element cell property|Tl|thallium  |31|p-block|Primordial}}
| {{element cell property|Pb|lead      |34|p-block|Primordial}}
| {{element cell property|Bi|bismuth   |91|p-block|Primordial}}
| {{element cell property|Po|polonium  |(136)|p-block|from decay}}
| {{element cell property|At|astatine  |233|p-block|from decay}}
| {{element cell property|Rn|radon     |(−70)|p-block|from decay}}
|-
! [[Period 7 element|7]]
| {{element cell property|Fr|francium     |(47)|s-block|from decay}}
| {{element cell property|Ra|radium       |(10)|s-block|from decay}}
| {{element cell-asterisk|2vert}}
| {{element cell property|Lr|lawrencium   |(−30)|d-block|Synthetic}}
| {{element cell property|Rf|rutherfordium|&nbsp;|d-block|Synthetic}}
| {{element cell property|Db|dubnium      |&nbsp;|d-block|Synthetic}}
| {{element cell property|Sg|seaborgium   |&nbsp;|d-block|Synthetic}}
| {{element cell property|Bh|bohrium      |&nbsp;|d-block|Synthetic}}
| {{element cell property|Hs|hassium      |&nbsp;|d-block|Synthetic}}
| {{element cell property|Mt|meitnerium   |&nbsp;|d-block|Synthetic}}
| {{element cell property|Ds|darmstadtium |&nbsp;|d-block|Synthetic}}
| {{element cell property|Rg|roentgenium  |(151)|d-block|Synthetic}}
| {{element cell property|Cn|copernicium  |(<0)|d-block|Synthetic}}
| {{element cell property|Nh|nihonium     |(67)|p-block|Synthetic}}
| {{element cell property|Fl|flerovium    |(<0)|p-block|Synthetic}}
| {{element cell property|Mc|moscovium    |(35)|p-block|Synthetic}}
| {{element cell property|Lv|livermorium  |(75)|p-block|Synthetic}}
| {{element cell property|Ts|tennessine   |(166)|p-block|Synthetic}}
| {{element cell property|Og|oganesson    |(8)|p-block|Synthetic}}
|-
| colspan="22"|<br />
|-
| colspan="4" {{element cell-asterisk|1|align=right}}
| {{element cell property|La|lanthanum   |54|f-block|Primordial}}
| {{element cell property|Ce|cerium      |55|f-block|Primordial}}
| {{element cell property|Pr|praseodymium|11|f-block|Primordial}}
| {{element cell property|Nd|neodymium   |9|f-block|Primordial}}
| {{element cell property|Pm|promethium  |(12)|f-block|from decay}}
| {{element cell property|Sm|samarium    |(16)|f-block|Primordial}}
| {{element cell property|Eu|europium    |11|f-block|Primordial}}
| {{element cell property|Gd|gadolinium  |(13)|f-block|Primordial}}
| {{element cell property|Tb|terbium     |13|f-block|Primordial}}
| {{element cell property|Dy|dysprosium  |1|f-block|Primordial}}
| {{element cell property|Ho|holmium     |(33)|f-block|Primordial}}
| {{element cell property|Er|erbium      |(30)|f-block|Primordial}}
| {{element cell property|Tm|thulium     |99|f-block|Primordial}}
| {{element cell property|Yb|ytterbium   |(−2)|f-block|Primordial}}
|-
| colspan="4" {{element cell-asterisk|2vert|align=right}}
| {{element cell property|Ac|actinium    |(34)|f-block|from decay}}
| {{element cell property|Th|thorium     |(113)|f-block|Primordial}}
| {{element cell property|Pa|protactinium|(53)|f-block|from decay}}
| {{element cell property|U |uranium     |(51)|f-block|Primordial}}
| {{element cell property|Np|neptunium   |(46)|f-block|from decay}}
| {{element cell property|Pu|plutonium   |(−48)|f-block|from decay}}
| {{element cell property|Am|americium   |(10)|f-block|Synthetic}}
| {{element cell property|Cm|curium      |(27)|f-block|Synthetic}}
| {{element cell property|Bk|berkelium   |(−165)|f-block|Synthetic}}
| {{element cell property|Cf|californium |(−97)|f-block|Synthetic}}
| {{element cell property|Es|einsteinium |(−29)|f-block|Synthetic}}
| {{element cell property|Fm|fermium     |(34)|f-block|Synthetic}}
| {{element cell property|Md|mendelevium |(94)|f-block|Synthetic}}
| {{element cell property|No|nobelium    |(−223)|f-block|Synthetic}}
|-
| colspan=19 style="text-align:left;" | '''Legend'''
|-
| colspan=19 style="text-align:left;" |Values are in [[Joule per mole|kJ/mol]], rounded
|-
| colspan=19 style="text-align:left;" | For the equivalent in eV, see: [[Electron affinity (data page)]]
|-
| colspan=19 style="text-align:left;" | [[Bracket|Parentheses or Round brackets()]] denote predictions
|-
| colspan=19 | 
{{periodic table legend
|theme1=Occurrence
|theme2=Block|unknown2=no}}
|}