Which of the following hydrate is diamagnetic ?

Options

A. `[Mn(H_(2)O_(6))]^(2+)`
B. `[Cu(H_(2)O)_(6)]^(3+)`
C. `[Co(H_(2)O)_(6)]^(3+)`
D. `[Co(H_(2)O)_(6)]^(2+)`

Answer

C

Explanation

`[Mn(H_(2)O)_(6)]^(3+)` : Octahatral, Five unpaired electrons-paramagenetic
`[Cu(H_(2)O)_(6)]^(3+)` : Octahedral , Two unpaired electrons-paramagnetic
`[Co(H_(2)O)_(6)]^(2+)` : Octahedral , No unpaired electron-diamagnetic
`[Co(H_(2)O)_(6)]^(2+)` : Octahedral , Three unpaired electrons-paramagnetic.
`Mn^(2+)` (Z = 25) : `[Ar]^(18)3d^(5)` ,
`Cu^(3+)` (Z = 29) : `[Ar]^(18)3d^(8)` ,
`Co^(3+)` (z = 27) : `[Ar]^(18)3d^(6)` ,
`Co^(2+)` (z = 27) : `[Ar]^(18)3d^(7)`