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

Jan 2, 2017

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

#### Explanation:

Consider oxidation reactions of the alkali metals:

$N a \left(s\right) \rightarrow N {a}^{+} + {e}^{-}$

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 $1.16 \times {10}^{-} 10 \cdot m$. The metallic radius of sodium metal is $1.80 \times {10}^{-} 10 \cdot m$.

(Note that I use ${10}^{-} 10 \cdot m$ units because the $\text{Angstrom}$ 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?