Group 16 elements are also called

For the reaction, $\mathrm{Br}_2+\mathrm{F}_2$ (excess) ⟶ P , the molecular formula and structure of P , respectively, are

In the following reaction, $a, b, p, q, r$ and $s$ are $a \mathrm{XeF}_4+b \mathrm{H}_2 \mathrm{O} \longrightarrow p \mathrm{Xe}+q \mathrm{XeO}_3+r \mathrm{HF}+s \mathrm{O}_2$

The increase in the atomic radii of the third (5d) series of transition elements is very small, which may be accounted for the filling of ' $X$ ' orbitals before ${ }^{\prime} Y^{\prime}$ orbitals $X$ and $Y$ are