Question

Three elements 'X', 'Y' and 'Z' have atomic numbers $7,8,$ and $9$ respectively. Write the formula of the compound formed when 'X' combines with 'Z'.

Answer 1

The elements $X,Y$ and $Z$ are nitrogen, oxygen and fluorine respectively. The valency of nitrogen is $3$ and that of fluorine is $1$.

$N$ $F$

$3$ $1$ ( by Criss cross method )

$X{Z}_3$ or $N{F}_3$ is the formula of the compound formed when $X$ combines with $Z$.