Question

Among the following compounds which is both paramagnetic and coloured?

• A. $K_{2}Cr_{2}O_{7}$
• B. $[Co(SO_{4})]$
• C. $(NH_{4})_{2} [TiCl_{6}]$
• D. $K_{3} [Cu(CN)_{4}]$

Answer 1

Answer: (B)

$[Co(SO_{4})]$

Answer 2

In $[Co(SO_{4})]$, the oxidation state of Co is $+2$. Configuration of $Co^{2+} = 3d^{7}$ , it has unpaired electrons in $3d$-orbitals so it is paramagnetic. Because of incompletely filled $d$-orbitals it is coloured