The number of paramagnetic species from the following is Ni ( CN ) 4 2 - , Ni ( CO ) 4 , NiCl 4 2 - Fe ( CN ) 6 4 - , Cu NH 3 4 2 + Fe ( CN ) 6 3 -  and  Fe H 2 O 6 2 +

Step-by-step solution

Ni ( CN ) 4 2 - : Ni + 2 = It is diamagnetic as CN - is a strong field ligand and forces electron pairing. Ni ( CO ) 4 : Ni = It is diamagnetic as carbonyl group is a strong field ligand and forces electron pairing. NiCl 4 2 - : Ni 2 + = It is paramagnetic as chloride group is a weak field ligand. Fe ( CN ) 6 4 - : Fe 2 +   : - It is diamagnetic as – CN is a strong field ligand which causes pairing of electrons. Cu NH 3 4 + 2 : Cu + 2 ⇒ Here Copper ion has one unpaired electron, thus it is paramagn