Why is there a large increase between th first and second ionization energies of the alkali metals?

1 Answer
Jan 9, 2017

Because the valence shell of the alkali metal contains ONE electron only........


Two factors are important here. #"A priori"# we would expect that it would be harder to remove an electron from a cation than from a neutral species. This is from simple considerations of electrostatics.

Neverthless, the alkali metals metals contain only the one valence electron. Ionization of an #"M"^+# ion requires that the electron be removed from an inner shell, that is closer to the metal nucleus, and therefore much more strongly held:

#M(g) + Delta_1rarrM^(+)(g) + e^(-)#

#M^(+)(g) + Delta_2rarrM^(2+)(g) + e^(-)#


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