What is the number of sigma $(\sigma)$ bonds in $P_4O_{10}$?

Which of the following compounds is not hypovalent but completes its octet?

Define the octet rule. Write its significance and limitations.

Which of the following contains both covalent and ionic bonds?

In which of the following compounds is the octet complete $(C)$ or incomplete $(IC)$ for all atoms?
$Al_2Cl_6$ $-$ $Al_2(CH_3)_6$ $-$ $AlF_3$ $-$ Dimer of $BeCl_2$ $-$ Dimer of $BeH_2$
(Note: $C$ for complete octet and $IC$ for incomplete octet.)

Fill in the blanks given below:
$(i)$ The two theories based on the principles of quantum mechanics are ........ and ......... .
$(ii)$ The electronic configuration of carbon in the excited state is ........... .
$(iii)$ Through the combination of atomic orbitals,....... are formed.
$(iv)$ The ${\rm{CH}}_4$ molecule has a .......... shape.