Which of the following elements has a valency of zero?

Which of the following elements exhibits a valency of $2$?

Consider the elements:
$Cs, Ne, I$ and $F$
$(a)$ Identify the element that exhibits only negative oxidation state.
$(b)$ Identify the element that exhibits only positive oxidation state.
$(c)$ Identify the element that exhibits both positive and negative oxidation states.
$(d)$ Identify the element which exhibits neither the negative nor does the positive oxidation state.

The oxidation state of $+1$ for phosphorus is found in:

The general formula of the compound formed when a metal $(M)$ of group $1$ reacts with a non-metal $(X)$ of group $16$ is:

Consider the following information about elements $P$ and $Q$:

Element	Period and Group
$Q$	Period $2$,Group $15$
$P$	Period $3$,Group $2$

Then the formula of the compound formed by $P$ and $Q$ elements is: