Thus, in $\mathrm{NO}_{3}$, the central atom is $sp ^2$ hybridized and it has trifocal planar geometry. $\ln \mathrm{H}_{3} \mathrm{O}^{+}$

$\mathrm{H}=\frac{1}{2}[6+3-1+0]=4$

Thus, $\mathrm{O}$ is $s p^{3}$ hybridised in $\mathrm{H}_{3} \mathrm{O}^{+}$ and $\mathrm{H}_{3} \mathrm{O}^{+}$ has pyramidal geometry due to the presence of one lone pair of electrons.