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 : $NH_3 > SbH_3 > AsH_3 > PH_3$

Superphosphate of lime is

Due to $p\pi - p\pi$ bonding interactions, nitrogen forms $N_2$ but phosphorus forms $X$ and does not form a diatomic molecule. Identify $X$.

The relative stability of $+1$ oxidation state of group $13$ elements follows the order:

Choose the correct statements about the hydrides of group $15$ elements.
$A$. The stability of the hydrides decreases in the order $NH_3 > PH_3 > AsH_3 > SbH_3 > BiH_3$
$B$. The reducing ability of the hydrides increases in the order $NH_3 < PH_3 < AsH_3 < SbH_3 < BiH_3$
$C$. Among the hydrides,$NH_3$ is strong reducing agent while $BiH_3$ is mild reducing agent.
$D$. The basicity of the hydrides increases in the order $NH_3 < PH_3 < AsH_3 < SbH_3 < BiH_3$
Choose the most appropriate from the option given below:

Which of the following elements shows a maximum valency of $5$?