$\mathrm{F}-\mathrm{Be}-\mathrm{F}$ is a linear molecule but $\mathrm{H}-\mathrm{O}-\mathrm{H}$ is angular. Explain.

In case of bond formation in acetylene molecule: State number of sigma and pi bonds formed.

In case of bond formation in acetylene molecule: Name the type of hybridisation.

Define bond length.

Predict the shape and bond angles in the following molecules: ${\mathrm{CF}}_4$.

Predict the shape and bond angles in the following molecule: ${\mathrm{NF}}_3$.

Predict the shape and bond angles in the molecule: $\mathrm{HCN}$.

Predict the shape and bond angle in the following molecule: ${\mathrm{H}}_2\mathrm{S}$.