If three elements $A, B, C$ crystalise in a cubic solid lattice with $B$ atoms at the cubic centres, $C$ aton at the centre of edges and A atoms at the corners, then formula of the compound is

Which of the following oxides is paramagnetic?

How many electrons are needed to reduce $\mathrm{N}_2$ to $\mathrm{NH}_3 ?$

The bond order of $\mathrm{HeH}^{+}$is