A bond in which an electron pair is unequally shared by two atoms is:

Polar covalent bond

Explanation: Electron sharing is usually attributed to covalent bonding as different from the actual transfer of electron from one atom to another which is a feature of Electrovalent bonding of atoms. In covalent bond, unstable pair of atoms share electron in other to reach their octet state. However, a Polar covalent bond occurs when the shared pair of electrons is unequal below between the sharing atom with one atom having a greater pull on the electron than the other. A common example of Polar covalent bond is the bonding between hydrogen and oxygen in the formation of water molecule (H2O) with

oxygen, selenium, tellurium, and polonium.

they're all from the same group as sulfur (group 16).