The size of the following species increases in the order

Options

A. `A1 lt Mg^(2+) lt F^(-) lt Na^(+)`
B. `F^(-) lt A1 lt Na^(+) lt Mg^(2+)`
C. `Mg^(2+) lt Na^(+) lt F^(-) A1`
D. `Na^(+) lt A1 lt F^(-) lt Mg^(2+)`

Answer

C

Explanation

`F^(-), Na^(+)`, and `Mg^(2+)` are isoelectronic species, their size increases with decrease of nuclear charge. Thus, the correct order of size is
`Mg^(2+)(Z = 12) lt Na^(+) (Z = 10) lt F^(-) (Z = 9)`