According to VSEPR theory, the repulsive forces between lone pair and lone pair are grater than between lone pair and bond pair which are further greater than bond pair and bond pair.

sp³d² hybridisation (octahedral geometry, square planar shape)

X = $$1 \over 2$$ (VE + MA - c + a)

For $$NO^+_2$$, X = $$1 \over 2$$ (5 + 0 - 1) = 2, so sp hybridisation

For $$NO^-_3$$, X = $$1 \over 2$$ (5 + 0 + 1) = 3, so sp² hybridisation

For $$NH^+_4$$, X = $$1 \over 2$$ (5 + 4 - 1) = 4, so sp³ hybridisation