Question
Question: Why is \( {H_2}O \) a polar bond \( ? \)...
Why is H2O a polar bond ?
Solution
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 H2O=3.5−2.1=1.4
Hence, H2O 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.