Question

Why is $ {H_2}O $ a polar bond $ ? $

Answer 1

Hint: First we have to know a polar bond is a covalent bond between two atoms where a pair of electrons is unequally distributed between two atoms. Nonpolar bond is a covalent bond where two atoms share a pair of electrons with each other. To find the given molecule is polar or not, we need to find its electronegativity difference between two atoms in a given molecule.

Complete answer:
Electronegativity, is the tendency for an atom of a given element to attract shared electrons (or electron density) in a covalent bond. Electronegativity of an atom is affected by both its atomic number and the size of the atom.
In a given molecule,
If the electronegativity difference between two atoms is greater than $ 2 $ , then the bond is ionic and the molecule is fully charged.
If the electronegativity difference between two atoms lies between $ 0.4 $ and $ 2 $ , then the bond is polar and the molecule is partially charged.
If the electronegativity difference between two atoms is less than $ 0.4 $ , then the bond is nonpolar and the molecule is electrically symmetrical (no charge).
Since we know the electronegativity value of hydrogen is $ 2.1 $ , while the electronegativity value of oxygen is $ 3.5 $ . Then the electronegativity difference between hydrogen and oxygen of $ {H_2}O = 3.5 - 2.1 = 1.4 $
Hence, $ {H_2}O $ is a polar.

Note:
The covalent bonds are three types namely polar and nonpolar. Also, a sigma bond is the strongest type of covalent bond. The covalent bonds form when electrons are shared between two nonmetals, whereas ionic bonds form when electrons exchange between a nonmetal and a metal.