Among the species given below, the total number of diamagnetic species is ____. H atom, $\mathrm{NO}_{2}$ monomer, $\mathrm{O}_{2}{ }^{-}$(superoxide), dimeric sulphur in vapour phase, $\mathrm{Mn}_{3} \mathrm{O}_{4},\left(\mathrm{NH}_{4}\right)_{2}\left[\mathrm{FeCl}_{4}\right],\left(\mathrm{NH}_{4}\right)_{2}\left[\mathrm{NiCl}_{4}\right], \mathrm{K}_{2} \mathrm{MnO}_{4}, \mathrm{~K}_{2} \mathrm{CrO}_{4}$

JEE Advanced · 2018 · 20 May 2018 · Paper 1 · Coordination Compounds

Among the species given below, the total number of diamagnetic species is ____.

H atom,

NO_{2}

monomer,

O_{2}^{-}

(superoxide), dimeric sulphur in vapour phase,

Mn_{3} O_{4}, (NH_{4})_{2} [FeCl_{4}], (NH_{4})_{2} [NiCl_{4}], K_{2} MnO_{4}, K_{2} CrO_{4}

Answer: 1

Analyzing each species for unpaired electrons:

H atom: 1 unpaired electron → paramagnetic
** $NO_{2}$ monomer**: Odd electron species → paramagnetic
** $O_{2}^{-}$ (superoxide)**: 1 unpaired electron in π* antibonding orbital → paramagnetic
** $S_{2}$ (dimeric sulphur)**: Like $O_{2}$ , has 2 unpaired electrons in π* antibonding orbitals → paramagnetic
** $Mn_{3} O_{4}$ **: Contains $Mn^{2 +}$ and $Mn^{4 +}$ , both have unpaired electrons → paramagnetic
** $(NH_{4})_{2} [FeCl_{4}]$ **: $Fe^{2 +}$ in weak field (tetrahedral) has 4 unpaired electrons → paramagnetic
** $(NH_{4})_{2} [NiCl_{4}]$ **: $Ni^{2 +}$ in weak field (tetrahedral) has 2 unpaired electrons → paramagnetic
** $K_{2} MnO_{4}$ **: $Mn^{6 +}$ has 1 unpaired electron → paramagnetic
** $K_{2} CrO_{4}$ **: $Cr^{6 +}$ has electronic configuration [Ar]3d⁰, no unpaired electrons → diamagnetic

Only

K_{2} CrO_{4}

is diamagnetic.

Answer: 1

JEE Advanced · 2018 · 20 May 2018 · Paper 1 · Numerical answer