Understanding:
• Water molecules are polar and hydrogen bonds form between them
Water is made up of two hydrogen atoms covalently bonded to an oxygen atom (molecular formula = H2O)
While this covalent bonding involves the sharing of electrons, they are not shared equally between the atoms
- Oxygen (due to having a higher electronegativity) attracts the electrons more strongly
- The shared electrons orbit closer to the oxygen atom than the hydrogen atoms resulting in polarity
Water is described as being polar because it has a slight charge difference across the different poles of the molecule
- The oxygen atom is slightly negative (δ–) while the hydrogen atoms are slightly positive (δ+)
This charge difference across the molecule (dipole) allows water to form weak associations with other polar molecules
- The slightly negative poles (δ–) will attract the slightly positive poles (δ+) of other molecules, and vice versa
When a δ+ hydrogen atom is attracted to a δ– fluorine, oxygen or nitrogen atom of another molecule, it forms a hydrogen bond
- Hydrogen bonds are relatively stronger than other polar associations due to the high electronegativity of F, O and N