If the dipole moment of an $MX_3$ molecule is zero,then the orbitals used by $M$ $(atomic\ number < 21)$ in sigma bonding are ....

Which of the following molecules contains a bond formed by the overlap of $sp$ and $sp^3$ hybrid orbitals?

Which of the following is an incorrect relation based on Bent's rule?

The ion that has $sp^3d^2$ hybridization for the central atom is

The carbon atoms in an acetylene molecule are in which state of hybridisation?

Fill in the blanks:
$(i)$ Based on the type of overlapping,covalent bonds are classified into ........ and .......... .
$(ii)$ The bond formation involving hybrid orbitals is called ............. .
$(iii)$ The type of hybridization observed in the $C_2H_6$ molecule is ........... .
$(iv)$ The type of hybridization observed in the $BrF_5$ complex is ............... .