Write the valency of phosphorus in ${\mathrm{PH}}_3$.

Write the valency of sulphur in ${\mathrm{SF}}_6$.

Write the valency of fluorine in ${\mathrm{CaF}}_2$.

Write the valency of nitrogen in ${\mathrm{N}}_2{\mathrm{O}}_3$.

An element 'X' has a valency 1. Write the chemical formula of its phosphide.

An element 'X' has valency 1. Write the chemical formula of its chloride.

An element 'X' has a valency 1. Is element 'X' a metal or a non-metal?