A solution of ` [Ni(H_2O)_6]^(2+) ` is green whereas a solution of ` [Ni(CN_4)]^(2-) ` is colorless -Explain.

Explanation

Complex I:
` [Ni (H_2O]_6^(2+) `
The outer electronic configuration of Ni is ` 3d^(8) 4s^(2) ` Ni atoms

` Ni^(2+) ion 3d^(8) 4s^(0)`

Ni in ` [Ni (H_2O )_6]^(2+)`
` H_2O` is a weak field ligand so pairing does occurs

Hybridisaton is `sp^(3) d^(2)`
Two unpaired electrons so coloured and paramagnetic in nature
Complex II:
` [Ni (CN)_4]^(2-)`
The outer electronic configuration of Ni is `3d^(8) 4s^(2)`
` (##SUR_CHE_XII_V01_C05_E02_025_S04.png" width="80%">
Ni in ` [Ni (CN)_4]^(2-)`
` CN^(-) ` is strong field ligand so pairing occurs
` (##SUR_CHE_XII_V01_C05_E02_025_S05.png" width="80%">
Hybridisation is `dsp^(2)` No unpaired electrons so colourless and diamaganetic nature.