How does concentrated $HNO_3$ react with aluminium?

The purest form of $N_2$ is prepared by the thermal decomposition of:

The atomic number of nitrogen is $7$. What will be the atomic number of the third member of the nitrogen family?

The molecular formula of an acid of phosphorus is $H_3PO_2$. What are its name and basicity,respectively?

Which is the correct sequence in the following properties? For the correct order mark $(T)$ and for the incorrect order mark $(F)$.
$(a)$ Lewis acidity order : $SiF_4 < SiCl_4 < SiBr_4 < SiI_4$
$(b)$ Melting point : $NH_3 > SbH_3 > AsH_3 > PH_3$
$(c)$ Boiling point : $NH_3 > SbH_3 > AsH_3 > PH_3$
$(d)$ Dipole moment order : $NH_3 > SbH_3 > AsH_3 > PH_3$

What are $X$ and $Y$, respectively in the following reactions?
$Au + \text{aqua regia} \longrightarrow AuCl_4^{-} + H_2O + X$
$Pt + \text{aqua regia} \longrightarrow PtCl_6^{2-} + H_2O + Y$