If the electronic configuration of $M = 2, 8, 3$ and that of $A = 2, 8, 7$,the formula of the compound is

The valency of inert gases is

In view of the signs of $\Delta_{r} G^{\circ}$ for the following reactions:
$PbO_2 + Pb \longrightarrow 2 PbO, \Delta_{r} G^{\circ} < 0$
$SnO_2 + Sn \longrightarrow 2 SnO, \Delta_{r} G^{\circ} > 0$
Which oxidation states are more characteristic for lead and tin?

The maximum valency of an element with atomic number $7$ is

What is the stock notation of Manganese dioxide?

Which of the properties remains unchanged on descending a group in the periodic table?