Is the radius of an ion always larger than the atomic radius of the original atom?

1 Answer
Jan 2, 2017

Absolutely not! Consider oxidation reactions of metals........


Consider oxidation reactions of the alkali metals:

#Na(s) rarr Na^+ + e^-#

We have removed the valence electron of an alkali metal. The ion, the oxidation product is MUCH smaller. TO illustrate the ionic radius of sodium ion in sodium chloride is #1.16xx10^-10*m#. The metallic radius of sodium metal is #1.80xx10^-10*m#.

(Note that I use #10^-10*m# units because the #"Angstrom"# is the standard unit for crystallography, tho I cannot find the proper symbol, a capital A with a circle hat.)

Of course reduction of a non-metal to give an anion, will give a larger ionic radius than the atomic radius. Why so?