Which of the following ions is not isoelectronic with the other three ?

Options

A. `CO_3^(2-)`
B. `NO_3^-`
C. `SO_3^(2-)`
D. `BO_3^(3-)`

Answer

C

Explanation

Isoelectronic ions have the same electron configurations and therefore the same number of electrons .The atomic number of B.C.N.O. and S are 5,6,7,8 and 16 respectively. The number of electrons in `SO_3^(2-)` is 42, in other ions, 32.