Which of the following oxides of nitrogen is a blue solid?

The decrease in stability of the higher oxidation state in the $p-$block elements with an increasing atomic number is due to:

Identify the correct order$(s)$ among the following:
$a. NH_3 > PH_3 > AsH_3$ (Thermal stability)
$b. NH_3 < PH_3 < AsH_3$ (Reducing power)
$c. NI_3 > NBr_3 > NCl_3$ (Lewis basic character)
$d. N_2O_5 > P_2O_5 > As_2O_5$ (Acidic character)
Select the correct option:

The strongest base is

The number of $P-O-P$ bonds in $H_4P_2O_7$,$(HPO_3)_3$ and $P_4O_{10}$ are respectively.

Nitrogen forms $N_2$,but phosphorus forms $P_2$,which quickly converts into $P_4$. The reason for this is: