Which of the following is an amphoteric oxide?

Give the use of diamond.

Explain the following:
$(a)$ $CO_2$ is a gas whereas $SiO_2$ is a solid.
$(b)$ Silicon forms $SiF_6^{2-}$ ion whereas corresponding fluoro compound of carbon is not known.

The stability of dihalides of $Si, Ge, Sn$ and $Pb$ follows the sequence.

Which of the following compounds is the most volatile among $CH_4, SiH_4, GeH_4, SnH_4$?

Which one of the following is a correct set?