TS EAMCET 04 May 2019 Shift 2 Solved Paper

The nature of NiCl42− is paramagnetic because Cl is a weak ligand and two unpaired electrons remains in exciting state.
The nature of Ni(CN)42− is diamagnetic because CN is a strong ligand and no unapired electrons are leftin the excited state.
In[Cu(H2O)6]2+,Cu2+ one unpaired electron is present therefore it is paramagnetic.
In[Fe(H2O)6]2+,Fe2+4 unpaired electrons are present and produce strong paramagnetic nature.
Therefore, the order is,
Ni(CN)42−<[Cu(H2O)6]2+<NiCl42−<[Fe(H2O)6]2+