Which of the following statements are correct ?
`(i)` Amongs `O_(2),O_(2)^(+),O_(2)^(-)` and `O_(2)^(2-),O_(2)^(+)` has the greatest stability.
`(ii)` Double bond in `C_(2)` consists of both Pi `(pi)` bonds because of the presence of four electrons in two pi molecule orbitals.
`(iii)` Amongst `B_(2),C_(2),N_(2)` and `O_(2)`, mixing of `2s-2p` orbitals takes palace only in `N_(2)` molecule.
`(iv)` Isoelectronic molecules and ions have identical bond order.

Options

A. `(i)` and `(ii)` only
B. `(ii)` and `(ii)` only
C. `(i)` and `(iii)` only
D. `(i),(ii)` and `(iv)` only

Answer

4

Explanation

`(i)O_(2)=(10-6)/(2)=2," "O_(2)^(+)=(10-5)/(2)=2.5`
`O_(2)^(-)=(10-7)/(2)=1.5," "O_(2)^(2-)=(10-8)/(2)=1`
Bond strength `prop` Bond order
`(ii) sigma1s^(2)sigma^(**)1s^(2)sigma 2s^(2) sigma^(**)2s^(2)pi 2px^(2)=pi 2p y^(2)," "Cunderset(pi)overset(pi)(=)C`
`(iii)` Mixing of `2s-2p` orbitals takes place in `N_(2),B_(2)` and `C_(2)` molecules. No mixing os `2s-2p` orbitals occurs in `O_(2)` molecules.
`(iv)` `N_(2),CO` and `NO^(+)` having 14 electrons possess bond order 3.