Which metal has a greater tendency to form metal oxide?

What is zeolite among the following?

The atomic radii of alkali metals $(M)$ lie in the order $Li < Na < K < Rb$,but the radii of $M^{+}$ ions in aqueous solution lie in the reverse order $Li^{+} > Na^{+} > K^{+} > Rb^{+}$. What is the reason for this reverse order (on going from $Li$ to $Rb$)?

Alkali metals react with water to form hydroxides and release hydrogen gas. This is because:

Identify the correct statement from the following.

$KO_2$ (potassium superoxide) is used in oxygen cylinders in space and submarines because it