Under which of the following conditions can active nitrogen be produced by passing $N_2$ gas through an electric spark?

The number of $P-O-P$ bonds in cyclic metaphosphoric acid is ....

The purest form of $N_2$ is prepared by the thermal decomposition of:

Assertion : Molecular nitrogen is less reactive than molecular oxygen.
Reason : The bond length of $N_2$ is shorter than that of oxygen.

Given below are two statements:
Statement $I$: Like nitrogen that can form ammonia,arsenic can form arsine.
Statement $II$: Antimony cannot form antimony pentoxide.
In the light of the above statements,choose the most appropriate answer from the options given below:

The atomic number of $N$ is $7$. The atomic number of the $3$rd member of the nitrogen family is: