Fill in the blanks given below:
$(i)$ The energy required to completely separate one mole of a solid ionic compound into its gaseous constituent ions is called ........... .
$(ii)$ The angle formed between the orbitals containing bonding electrons around the central atom is called ........... .
$(iii)$ The energy required to break one mole of bonds is called ........... .
$(iv)$ The $VSEPR$ theory was proposed by scientists ............ and ........... .