Among the following,the number of elements showing only one non-zero oxidation state is $O, Cl, F, N, P, Sn, Tl, Na, Ti$.

Which of the properties remains unchanged on descending a group in the periodic table?

The valency (oxidation state) of phosphorus in $H_3PO_4$ is

$A$ compound contains three elements $A$,$B$ and $C$. If the oxidation states are $A = +2$,$B = +5$ and $C = -2$,the possible formula of the compound is

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.

An element $(A)$ occurs in the short period having electronic configuration $ns^2 np^1$. The formula of its oxide will be