The correct order of the spin-only magnetic moment of metal ions in the following low spin complexes, ${[V(CN)_6]^{4-}, [Fe(CN)6]^{4-}, [Ru (NH3)6]^{3+},}$ and ${[Cr(NH3)6]^{2+}}$, is :
Solution:- $( A ) V ^{2+}> Cr ^{2+}> Ru ^{3+}> F e ^{2+}$ According to equations, all the complexes are low spin. No. of Complex $\quad$ Configuration unpaired electrons $\left[\begin{array}{lll}{\left[ V ( CN )_{6}\right]^{4-}} & t _{2 g }^{3} e _{ g }^{0} & 3\end{array}\right.$ No. ot Complex Configuration unpaired electrons $\left[ V ( C N )_{6}\right]^{4-} \quad t _{ 2 g }^{3} e _{ g }^{0}$ 3 $\left.\left[ C r ( N H )_{3}\right)_{6}\right]^{2+} t _{2 g }^{4} e _{ g }^{0}$ 2 $\left[ R u \left( N H _{3}\right)_{6}\right]^{3+} t _{2 g }^{5} e _{ g }^{0}$ 1 $\left[ F e ( C N )_{6}\right]^{4-} t _{2 g }^{6} e _{ g }^{0}$ 0
Multiple oxidation states- The oxidation states of d block elements show very few energy gaps; therefore, they exhibit many oxidation states. Also, the energy difference between s and d orbital is very less. Therefore both the electrons are involved in ionic and covalent bond formation, which ultimately leads to multiple oxidation states.
Formation of complex compounds- Ligands show a binding behavior and can form so many stable complexes with the help of transition metals. This property is mainly due to:
Availability of vacant d orbitals.
Comparatively small sizes of metals.
Hardness- Transition elements are tough and have high densities because of the presence of unpaired electrons.
Melting and boiling points- Melting and boiling points of transition are very high because of the presence of unpaired electrons and partially filled d orbitals. They form strong bonds and have high melting and boiling points.
Atomic radii- The atomic and ionic radius of the transition elements decreases as we move from Group 3 to group 6. However, it remains the same between group 7 and group 10, and from group 11 to group 12 increases.
Ionization enthalpy- The ionization enthalpies of the transition elements are generally on the greater side as compared to the S block elements