Octet Rule Chemistry Example 2

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

Example 2

medium
Use the octet rule to explain why sodium forms Na+\text{Na}^+ and chlorine forms Cl−\text{Cl}^- when they react to form NaCl.

Solution

  1. 1
    Sodium has 1 valence electron (electron configuration 2, 8, 1). Losing this electron gives Na+\text{Na}^+ with configuration 2, 8 — a full octet in the outer shell.
  2. 2
    Chlorine has 7 valence electrons (2, 8, 7). Gaining 1 electron gives Cl−\text{Cl}^- with configuration 2, 8, 8 — a full octet.
  3. 3
    Both ions achieve noble gas configurations: Na+\text{Na}^+ matches neon, Cl−\text{Cl}^- matches argon. The electrostatic attraction between these oppositely charged ions forms the ionic bond in NaCl.

Answer

Na loses 1e−(octet as Ne),  Cl gains 1e−(octet as Ar)\text{Na loses 1e}^- \text{(octet as Ne)},\; \text{Cl gains 1e}^- \text{(octet as Ar)}
The octet rule explains why certain ion charges are common. Group 1 metals always form +1 ions and Group 17 nonmetals always form -1 ions because these charges allow them to achieve stable octets.

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 3 medium

Use the octet rule to explain why oxygen forms two covalent bonds in a water molecule ([formula]).

Example 4 hard

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

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