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

The number of six-membered carbon rings and five-membered carbon rings present in Buckminsterfullerene are $x$ and $y$ respectively. The sum of $x$ and $y$ is:

Which of the following oxides is amphoteric?

Given below are two statements:
Statement $I$ : $SiO_2$ and $GeO_2$ are acidic while $SnO$ and $PbO$ are amphoteric in nature.
Statement $II$ : Allotropic forms of carbon are due to property of catenation and $p \pi-d \pi$ bond formation.
In the light of the above statements,choose the most appropriate answer from the options given below:

Explain the difference in properties of diamond and graphite on the basis of their structures.

The gas that cannot be collected over water is: