Question

The common features of the species N22– , O2 and NO– are :

• A. Bond order three and isoelectronic.
• B. Bond order two and isoelectronic.
• C. Bond order three but not isoelectronic.
• D. Bond order two but not isoelectronic.

Answer 1

Answer: (B)

Bond order two and isoelectronic.

Answer 2

N22– : $\sigma$1s2 $\sigma$ *1s2 $\sigma$ 2s2 $\sigma$ *2s2 $\pi$2px2 $\pi$ 2py2 $\sigma$2pz2 $\pi$ 2px1 $\pi$ *2py1.

B.O. N22– = $\frac{10 - 6}{2}$ = 2.; B.O. O2 = $\frac{10 - 6}{2}$ = 2.

NO– isoelectronic with O2 so B.O. = $\frac{10 - 6}{2}$= 2.

All have same number of electrons (i.e. 16) so isoelectronic.