Which of the following will react with fluorine?

The element that does NOT exhibit allotropy is ______.

Which among the following group $15$ element forms most stable pentavalent compound?

The boiling points of the following hydrides follow the order of _____.

The least stable hydride of ${15}^{\mathrm{th} }$ group elements is ______.

Which element among the following does form $\mathrm{p\pi }-\mathrm{p\pi }$ multiple bonds?

In case of nitrogen, ${\mathrm{NCl}}_{\mathrm{3}}$ is possible but not ${\mathrm{NCl}}_{\mathrm{5}}$; while in case of phosphorous, ${\mathrm{PCl}}_{\mathrm{3}}$ as well as ${\mathrm{PCl}}_{\mathrm{5}}$ are possible. It is due to ______.

Ammonium dichromate on heating gives ______.

Which among the group $15$ elements does NOT exist as tetra atomic molecule?