The group $14$ elements $A$ and $B$ have the first ionisation enthalpy values of $708$ and $715 \ kJ \ mol^{-1}$ respectively. These values are the lowest among their group members. The nature of their ions $A^{2+}$ and $B^{4+}$ respectively is:

Give the name of the basic structural unit of silicates and provide its examples.

The $C-C$ bond length is maximum in?

Given below are two statements,one is labelled as Assertion $A$ and the other is labelled as Reason $R$.
Assertion $A$: Carbon forms two important oxides $- CO$ and $CO_2$. $CO$ is neutral whereas $CO_2$ is acidic in nature.
Reason $R$: $CO_2$ can combine with water in a limited way to form carbonic acid,while $CO$ is sparingly soluble in water.
In the light of the above statements,choose the most appropriate answer from the options given below:

$C_{60}$ contains:

The butter of tin is represented by