If M is element of actinoids series, the degree of complex...

M

is element of actinoids series, the degree of complex formation decreases in the order

Options

A $\mathrm{M}^{4+} \gt \mathrm{M}^{3+} \gt \mathrm{MO}_2^{2+} \gt \mathrm{MO}_2^{+}$
B $\mathrm{M}^{4+} \gt \mathrm{MO}_2^{2+} \gt \mathrm{M}^{3+} \gt \mathrm{MO}_2^{+}$
C $\mathrm{MO}_2^{+} \gt \mathrm{MO}_2^{2+} \gt \mathrm{M}^{3+} \gt \mathrm{M}^{4+}$
D $\mathrm{MO}_2^{2+} \gt \mathrm{MO}_2^{+} \gt M^{4+} \gt M^{3+}$

Correct answer

B. $\mathrm{M}^{4+} \gt \mathrm{MO}_2^{2+} \gt \mathrm{M}^{3+} \gt \mathrm{MO}_2^{+}$

Step-by-step solution

The higher the charge on the metal ion, smaller is the ionic size and more is the complex forming ability. Thus, the degree of complex formation decreases in the order

\mathrm{M}^{4+} \gt \mathrm{MO}_2^{2+} \gt \mathrm{M}^{3+} \gt \mathrm{MO}_2^{+}

The higher tendency of complex formation of

\mathrm{MO}_2^{2+}

as compared to

\mathrm{M}^{3+}

is due to high concentration of charge on metal atom M.

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