The correct decreasing order of negative electron gain enthalpy for $$\mathrm{C}, \mathrm{Ca}, \mathrm{Al}, \mathrm{F}$$ and $$\mathrm{O}$$ is

The group number of the element in the periodic table with the electronic configuration $$(\mathrm{n}-1) \mathrm{d}^2 \mathrm{~ns}^2$$. For $$n=4$$ is:

The increasing order of atomic radii of the following group 13 elements is

In the periodic table metals usually used as catalysts belong to