A certain element is a metalloid that forms an acidic oxide, `E_2 O_5`. Indentify the element.
(b) `N_2` makes up about `79 %` of the atmosphere, why do not animals use the more abundant `N_2` instead of `O_2` for the biological processes ?

Explanation

(a) Since the element forma an oxide with the formula, `E_2O_5`, it must be an element of group `15`. Group `15` has two metalloids namely As and `Sb`. Acidic character of pentoxides of group `15` decreases down the group. Hence `As_2 O_5` is acidic and `Sb_2 O_5` is amphoteric. Thus the element is As and the metalloid is `As_2 O_5`.
(b) Large amount of energy is needed by the animals for their movement and to maintain the body temperature. Hence, to obtain the energy, it is much easier to break `(O=O)` bond rather than `(N=N)` bond, since `(O=O)` bond is weaker as compared to `N=N` bond.