Question

Peroxide ion ……
(i) has five completely filled antibonding
molecular orbitals
(ii) is diamagnetic " " (iii) has bond order one
(iv) is isoelectronic with neon
Which of these are correct ?
A. (iii) and (iv)
B. (i) , (ii) and (v)
C. (ii) and (iii)
D. (i) and (v)

Answer 1

Correct Answer - C
Peroxide ion is `O_(2)^(2-)`
E.C. `sigma_(1s)^(2) sigma_(1s)^(**2)sigma_(2s)^(2)sigma_(2s)^(**2)sigma_(2p_(z))^(2)pi_(2p_(x))^(2)pi_(2p_(y))^(2)pi_(2p_(x))^(**2)pi_(2p_(y))^(**2)`
It tha four completely filled antibonding molecular
obitals . It is diamgnetic .
Bond order `= (1)/(2) (10 - 8) = 1`
Total electrons present = 18
Thus , it is not isoelectronic with neon `._ ""(10)Ne`
Hence , only option (ii) and (iii) are correct