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

`Na^+ = 11 - 1 = 10 e^(-), Mg^(2+) = 12 - 2 = 10 e^(-)`, i.e, have same no. of electrons.
`Al^(3+) = 13-3 = 10 e^(-) , O^(2-) = 8 + 1 = 9 e^(-)` i.e., do not have same no. of electrons.
`Na^(+) = 11 - 1 =10 e^(-) , O^(2-) = 8 + 2 = 10 e^(-)` i.e, have same no. of electrons.
`Na^(3-) = 7 + 3 = 10 e^(-), Cl^(-) = 17 + 1 = 18 e^(-)` i.e., do not have same no. of electrons.