Who gave the principle of $VSEPR$?

In which of the following conversions does a planar compound change into a non-planar compound?
$(a)$ $ClF_3 \rightarrow ClF_4^{-}$
$(b)$ $NH_2^{-} \rightarrow NH_4^{+}$
$(c)$ $I_3^{+} \rightarrow I_3^{-}$
$(d)$ $SO_2 \rightarrow SO_3$

Identify the structure of $XeF_4$ molecule from the following.

Apart from tetrahedral geometry,another possible geometry for $CH_4$ is square planar with the four $H$ atoms at the corners of the square and the $C$ atom at its centre. Explain why $CH_4$ is not square planar?

In which of the following is the $O-N-O$ bond angle maximum?

The number of molecules/ions that show linear geometry among the following is $.........$
$SO_2, BeCl_2, CO_2, N_3^{-}, NO_2, F_2O, XeF_2, NO_2^{+}, I_3^{-}, O_3$