The Lewis structure for water (H2O) illustrates how the atoms within the molecule are bonded together and which electrons are involved in the bonding.
To draw the Lewis structure for H2O, follow these steps:
- Start by counting the total number of valence electrons. Hydrogen (H) has 1 valence electron and oxygen (O) has 6 valence electrons. Since there are two hydrogen atoms, the total number of valence electrons is 1 x 2 + 6 = 8.
- Next, place the oxygen atom in the center because it is less electronegative than hydrogen. Then, surround it with the two hydrogen atoms.
- Connect each hydrogen atom to the oxygen atom with a single bond, which uses 2 of the available valence electrons, leaving you with 6 electrons.
- Now, distribute the remaining 6 electrons around the oxygen atom to satisfy the octet rule. Place three lone pairs (6 electrons) on the oxygen atom.
- The final structure shows that the oxygen atom is bonded to two hydrogen atoms with single bonds, and it has two lone pairs of electrons.
The resulting Lewis structure can be drawn as:
H | O — H
This structure shows that water is a bent molecule due to the two lone pairs of electrons on the oxygen atom, which repel the hydrogen atoms and create an angle that is approximately 104.5 degrees.