In which of the following pairs, the ions are iso-electronic ?

Options

A. `Na^(+) ,Mg^(2+)`
B. `Al^(3+) , O^(-)`
C. `Na^(+), O^(2-)`
D. `N^(3-),Cl^(-)`

Answer

A, C

Explanation

The ions involved have 10 electrons
`Na^(+)=(Z=11) 1s^(2)2s^(2)2p^(6)`
`Mg^(2+) (Z=12) 1s^(2)2s^(2)2p^(6)`
`O^(2-)(Z=8) 1s^(2)2s^(2)2p^(6)`.