Which pair of metals does not dissolve in nitric acid?

$HNO_3$ is produced in good yield by which of the following methods?

The three important oxidation states of phosphorus are

Which element of the $13^{th}$ group does not show the group oxidation state in its compounds?

In the hydrides of the nitrogen group,the $H-M-H$ bond angle gradually approaches $90^o$ as we move from $N$ to $Sb$. This indicates that gradually.....

White phosphorus catches fire in air to produce dense white fumes. This is due to the formation of