The least stable ion among the following is

Options

A. `Li^(Theta)`
B. `Be^(Theta)`
C. `Be^(Theta)`
D. `C^(Theta)`

Answer

B

Explanation

`Be^(Theta)` is least stable
(a) `Li(Z =3) rArr 2s^(1)`
(b) `B (Z =5) rArr 2s^(2) 2p^(1)`
`b^(Theta) rArr 2s^(2) 2p^(2)`
(c ) `Be (Z =4) rArr 2s^(2)`
`Be^(Theta) rArr 2s^(2) 2p^(1)`
(d) `C (Z =6) rArr 2s^(2) 2p^(2)`
`C^(Theta) rArr 2s^(2) 2p^(3)`
Half -filled or full -filled orbitals are more stable as compared to nearly half-filled orbitals. Therefore stability order is
`Li^(Theta) gt C^(Theta) gt B^(Theta) gtBe^(Theta)` .