The polar bond is a covalent bond (atoms share their electrons) where the electronegativity difference is not very big, compared to an ionic bond.
- First molecule (acetylene):
In this molecule, the triple bond between carbon atoms is nonpolar, because the bond occurs between equal atoms.
- Second molecule (hydrobromic acid):
The bond occurs between two atoms with a difference in the electronegativity, so this is a polar bond. In this molecule, the atom with more negative charge is the bromine (Br).
- Third molecule (ammonia):
The electronegativity difference between the nitrogen atom and the hydrogen atom makes it a polar bond, and the more negative atom is nitrogen (N).