Which process is used to determine the reactivity of a metal?

Give the formulae of the stable binary compounds that would be formed by the combination of the following pairs of elements:
$(a)$ $Mg$ and $N_{2}$
$(b)$ $Li$ and $O_{2}$
$(c)$ $Al$ and $Cl_{2}$
$(d)$ $K$ and $O_{2}$

Which acid is formed when sulfur dioxide reacts with water?

Which method/process is used to obtain aluminium from pure alumina?

$(i)$ Arrange the following metals in the order of their decreasing activities: Aluminium, Gold, Sodium, Copper.
$(ii)$ Give the reaction of aluminium powder with manganese dioxide on heating.

In the presence of which catalyst is sulphur dioxide heated at high temperature to form sulphur trioxide?