Question

The primary valency of 'Fe' in complex K4[Fe(CN)6] is​

Answer 1

Primary valence is the oxidation state of the central metal atom, whereas secondary valence is co-ordination number (Number of ligands attached to Central metal atom) of the central metal atom. Here the central metal atom is Fe

In K4[Fe(CN)6], oxidation state of Fe can be calculated by adding oxidation states of all molecules & equating with total charge of the molecule

Oxidation state of K & CN are +1 & -1 respectively. Total charge of molecule is 0. Let oxidation state of Fe be 'x'

∴4(+1)+x+6(−1)=0∴x=+2

Thus, oxidation state of Fe is +2

In K4[Fe(CN)6], 6 cyanide molecules are donating lone pair of electrons to Fe. Therefore, co-ordination number of Fe is 6