Because of lanthanoid contraction, which of the following pairs of elements have nearly the same atomic radii? (Numbers in the parenthesis are atomic numbers.)

It is because of the inability of $ns^2$ electrons of the valence shell to participate in bonding that

The reason for greater range of oxidation states in actinoids is attributed to

Which one of the following elements is unable to form $MF_6^{3-}$ ion?

Which one of the following ions exhibits d-d transition and paramagnetism as well?

Which of the following species is not stable?

Identify the incorrect statement.

Match the following:$$

The incorrect statement among the following is:

Zr (Z=40) and Hf (Z=72) have similar atomic and ionic radii because of:

Gadolinium has a low value of third ionisation enthalpy because of

Match List-I with List-II:

Taking stability as the factor, which one of the following represents the correct relationship?

Which one is an example of heterogeneous catalysis?

The stability of Cu$^{2+}$ is more than Cu$^{+}$ salts in aqueous solution due to -

Which of the following statements are incorrect?$\\$A. All the transition metals except scandium form MO oxides which are ionic.$\\$B. The highest oxidation number corresponding to the group number in transition metal oxides is attained in Sc$_2$O$_3$ to Mn$_2$O$_7. \\$C. Basic character increases from V$_2$O$_5$ to V$_2$O$_3. \\$D. V$_2$O$_5$ dissolves in acids to give VO$_4^{3-}$ salts.$\\$E. CrO is basic but Cr$_2$O$_3$ is amphoteric.