Question

The oxidation number, coordination number and magnetic moment in the following complex is: $\left[Cr\right(C_2{O}_4{)}_2(N{H}_3{)}_2{]}^{-}$

• A. $O.N.=+3,C.N.=6,M.M.=\sqrt{15}BM$
• B. $O.N.=-1,C.N.=6,M.M.=\sqrt{15}BM$
• C. $O.N.=+3,C.N.=6,M.M.=\sqrt{3}BM$
• D. $O.N.=+3,C.N.=6,M.M.=\sqrt{12}BM$

Answer 1

Answer: (A)

$O.N.=+3,C.N.=6,M.M.=\sqrt{15}BM$

Let $X$ be the oxidation number of chromium in

$\left[Cr\right(C_2{O}_4{)}_2(N{H}_3{)}_2{]}^{-}$

$X+2(-2)+2\left(0\right)=-1\Rightarrow X=+3$.

Thus the oxidation number of chromium is $+3.$

In the complex two bidentate ligands and two monodentate ligands are attached. Thus the coordination number is six.

$C{r}^{3+}$ has $d^3$ outer electronic configuration and contains 3 unpaired electrons. Its magnetic moment is

${\mu }_{eff}=\sqrt{3(3+2)}B.M.=\sqrt{15}B.M.$.