Maximum bond angle is present in

Who first provided an explanation for the formation of chemical bonds in terms of electrons?

Identify the correct statement$(s)$ from the following:
$a$) Dipole moment of $NH_3$ is more than $NF_3$
$b$) $SF_4$ is square planar
$c$) $SnCl_4$ is more covalent than $SnCl_2$
$d$) $In_2SO_4$ sulphur atom has expanded octet

Select the correct order of bond angle.

$NH_2^-$,$NH_3$ and $NH_4^+$ do not show similarity in the following:

In which of the following pairs of species is the bond length as well as the bond energy of the $I^{st}$ species less than the $II^{nd}$ species?