The Structure of a Water Molecule
- A water molecule consists of one oxygen atom and two hydrogen atoms bonded together by covalent bonds.
- Covalent bonds form when atoms share electrons.
- However, in water, the sharing is unequal because oxygen is more electronegative than hydrogen.
Definition
Electronegativity
Electronegativity is an atom's ability to attract electrons in a bond.
Polarity: Unequal Charge Distribution
- Because oxygen pulls electrons closer:
- The oxygen atom develops a partial negative charge (δ−).
- The hydrogen atoms develop partial positive charges (δ+).
- This uneven charge distribution makes water a polar molecule, it has a positive end (hydrogen side) and a negative end (oxygen side).
Polarity Enables Hydrogen Bonding
- This polarity is what allows hydrogen bonds to form between water molecules:
- The δ+ hydrogen of one molecule is electrostatically attracted to the δ− oxygen of a neighboring molecules.
- Because opposite charges attract, these polar regions create weak intermolecular attractions.
- These attractions are hydrogen bonds.
Although a single hydrogen bond is weak, water molecules are small and numerous, allowing for a dense network of these bonds.
