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Information about Electron affinity

In chemistry, electron affinity is the amount of energy absorbed when an
electron is added to a neutral isolated gaseous atom to form a gaseous ion
with a 1- charge. It has a negative value if energy is released.

Most elements have a negative electron affinity. This means they do not
require energy to gain an electron; instead, they release energy. Atoms more
attracted to extra electrons have a more negative electron affinity.
Chlorine most strongly attracts extra electrons; radon most weakly attracts
an extra electron.

Although electron affinities vary in an chaotic manner across the table,
some patterns amerge. Generally, nonmetals have more negative electron
affinities than metals. However, the noble gases are an exception: they have
positive electron affinities.

Electron affinity is influenced by the octet rule. Group 1 elements
(hydrogen, lithium, sodium, potassium, rubidium, calcium, and francium) tend
to gain an electron and form -1 anions. The noble gases have a full octet,
and thus adding an extra electron requires large amounts of energy, but it
is possible.

 Group  1   2  3   4  5   6   7   8    9   10   11  12  13  14   15   16  17   18
 Period

   1    H                                                                      He
       -73                                                                     21

   2    Li Be                                           B    C   N    O    F   Ne
       -60 19                                          -27 -122  7   -141-328  29

   3    Na Mg                                           Al  Si   P    S   Cl   Ar
       -53 19                                          -43 -134 -72  -200-239  35

   4    K  Ca Sc  Ti  V   Cr Mn   Fe  Co   Ni   Cu  Zn  Ga  Ge   As   Se  Br   Kr
       -48 10 -18 -8 -51 -64  Ê  -16  -64 -112 -118 47 -29 -116 -78  -195-325  39

   5    Rb Sr  Y  Zr  Nb  Mo Tc   Ru  Rh   Pd   Ag  Cd  In  Sn   Sb   Te   I   Xe
       -47  Ê -30 -41-86 -72 -53 -101-110  -54 -126 32 -29 -116 -103 -190-295  41

   6    Cs Ba Lu  Hf  Ta  W  Re   Os  Ir   Pt   Au  Hg  Tl  Pb   Bi   Po  At   Rn
       -45  Ê  Ê   Ê -31 -79 -14 -106-151 -205 -223 61 -20  -35 -91  -183-270  41

   7    Fr Ra Lr  Rf  Db  Sg Bh   Hs  Mt   Ds  Uuu  UubUut  Uuq Uup  Uuh  Uus Uuo
       -44  Ê  Ê   Ê  Ê   Ê   Ê   Ê    Ê    Ê   Ê    Ê  Ê    Ê   Ê    Ê    Ê   Ê

              Periodic table of electron affinities, in kJ/mol

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