Distinguish between polar bonds and polar molecules.
To distinguish between polar bonds and polar molecules, it is important to understand what each term refers to.
1. Polar bond: A polar bond is a type of chemical bond that occurs when two atoms in a molecule have a significant difference in their electronegativity. Electronegativity is the ability of an atom to attract electron density towards itself in a chemical bond. In a polar bond, the atom with higher electronegativity pulls the shared electrons closer to itself, resulting in an uneven distribution of charge within the bond. This creates a partial positive charge on one atom and a partial negative charge on the other. For example, the bond between hydrogen (H) and oxygen (O) in a water molecule (H2O) is a polar bond because oxygen is more electronegative than hydrogen, causing the oxygen atom to pull the shared electrons closer to itself.
2. Polar molecule: A polar molecule is a molecule that has a net dipole moment due to the presence of polar bonds within it. In other words, for a molecule to be classified as polar, it must have polar bonds and its molecular geometry should be asymmetrical. The overall dipole moment of a polar molecule arises from the vector sum of the individual bond moments within it. In a polar molecule, the partial positive and partial negative charges do not cancel each other out, resulting in an uneven distribution of charge across the molecule. Water (H2O) is an example of a polar molecule because it has polar bonds and a bent molecular geometry, resulting in an overall dipole moment.
In summary, while polar bonds refer to the uneven distribution of charge within a specific bond, polar molecules have an overall uneven distribution of charge due to the presence of polar bonds and asymmetrical molecular geometry.