In ammonia molecule the bond angle is $107°$ and in water molecule it is $104°35\text{'}$, although in both the central atoms are ${\mathrm{sp}}^3$ hybridised explain.

Give reason for: Sigma$\left(\mathrm{\sigma }\right)$ bond is stronger than pi$\left(\mathrm{\pi }\right)$ bond.

Give reason for: $\mathrm{HF}$ is a polar molecule.

Give reason for: Carbon is a tetravalent in nature.

Identify the type of overlap present in ${\mathrm{H}}_2$.

Identify the type of overlap present in ${\mathrm{F}}_2$.

Identify the type of overlap present in$\mathrm{HF}$.