Octet Rule Chemistry Example 3

Follow the full solution, then compare it with the other examples linked below.

Example 3

medium
Use the octet rule to explain why oxygen forms two covalent bonds in a water molecule (H2O\text{H}_2\text{O}).

Solution

  1. 1
    Oxygen has 6 valence electrons and needs 2 more to complete its octet. Each hydrogen has 1 electron and needs 1 more for a duet.
  2. 2
    By forming one covalent bond with each of two hydrogen atoms, oxygen shares 2 pairs of electrons, reaching 8 total valence electrons (2 bonding pairs + 2 lone pairs).

Answer

O needs 2 electrons → forms 2 bonds with H → octet achieved\text{O needs 2 electrons → forms 2 bonds with H → octet achieved}
The number of covalent bonds an atom forms equals the number of electrons it needs to complete its octet: carbon forms 4, nitrogen forms 3, oxygen forms 2, and halogens form 1.

About Octet Rule

A chemical bonding principle stating that atoms tend to gain, lose, or share electrons in order to achieve a stable configuration of 8 electrons in.

Learn more about Octet Rule →

More Octet Rule Examples

Example 1 easy

State the octet rule and explain why atoms tend to follow it.

Example 2 medium

Use the octet rule to explain why sodium forms [formula] and chlorine forms [formula] when they reac

Example 4 hard

Identify two exceptions to the octet rule and give a specific molecular example of each.

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