The group number,number of valence electrons,and valency of an element with atomic number $15$,respectively,are

Assertion : $HClO_4$ is a stronger acid than $HClO_3$.
Reason : Oxidation state of $Cl$ in $HClO_4$ is $+VII$ and in $HClO_3$ is $+V$.

Which of the following elements has a valency of zero?

The number of elements among $O, Cl, F, N, P, Sn, Ti, K, Sc$ which show more than one non-zero oxidation state is:

Two elements $X$ and $Y$ have the following electronic configurations: $X = 1s^2, 2s^2 2p^6, 3s^2 3p^6, 4s^2$ and $Y = 1s^2, 2s^2 2p^6, 3s^2 3p^5$. The expected compound formed by the combination of $X$ and $Y$ is:

The number of valence electrons present in an element with atomic number $117$ is