What is the maximum covalency of the first-period elements? Why?

Explain the polar covalent bond with the help of a suitable example.

Which of the following is a non-polar bond?

According to Lewis and Langmuir,how and why is a covalent bond formed?

Which of the following molecules follows the octet rule?

The electronic configuration of three elements $A$,$B$,and $C$ are given below. The bond between $B$ and $C$ will be:
$A: 1s^2, 2s^2, 2p^6$
$B: 1s^2, 2s^2, 2p^6, 3s^2, 3p^3$
$C: 1s^2, 2s^2, 2p^6, 3s^2, 3p^5$