Question

Which of the following arrangements does not represent the correct order of the property stated against it?

• A. Sc <Ti <Cr <Mn : number of oxidation states
• B. V${}^{2+}$ <Cr${}^{2+}$ <Mn${}^{2+}$ <Fe${}^{2+}$: paramagnetic behavior
• C. Ni${}^{2+}$ <Co${}^{2+}$ < Fe${}^{2+}$ < Mn${}^{2+}$: ionic size
• D. Co${}^{3+}$ <Fe${}^{3+}$ <Cr${}^{3+}$ < Sc${}^{3+}$: stability in aqueous solution.

Answer 1

The correct option is B V${}^{2+}$ <Cr${}^{2+}$ <Mn${}^{2+}$ <Fe${}^{2+}$: paramagnetic behavior

Option a) – Number of oxidation states increases as we move from group 3 to group 7 in same period.

Option b) – V${}^{2+}$(3 unpaired electrons) %undefined Cr${}^{2+}$ ( 4 unpaired electrons) = Fe${}^{2+}$ (4 unpaired electrons) %undefined Mn${}^{2+}$ ( 5 unpaired electrons)

Option c)- Ionic size decreases from left to right in the same period.

Option d)- As the standard reduction potential value for the couple M${}^{3+}$/M${}^{2+}$ decreases, the stability of M${}^{3+}$ ion in aqueous solution increases. Thus, correct increasing order of stability of M${}^{3+}$ ions in aqueous solution is: Co${}^{3+}$ < Fe${}^{3+}$< Cr${}^{3+}$ <Sc${}^{3+}$.