Sodium and chlorine obey the octet rule when bonding by transferring an electron from sodium to chlorine, resulting in the formation of ions that have achieved stable electron configurations resembling noble gases.
The Octet Rule Explained
The octet rule states that atoms tend to gain, lose, or share electrons in order to achieve a full outer electron shell with eight electrons, which is the electron configuration of a noble gas. This full outer shell corresponds to a state of high stability.
Sodium's Role
- Sodium (Na) has an atomic number of 11, meaning it has 11 electrons.
- Its electron configuration is 1s²2s²2p⁶3s¹.
- Sodium has only one valence electron in its outermost shell (3s¹).
- To achieve an octet, sodium loses this single valence electron.
- By losing one electron, sodium becomes a positively charged ion (Na⁺) with a +1 charge.
- This also results in the electron configuration becoming 1s²2s²2p⁶, which is the same as the noble gas neon (Ne).
Chlorine's Role
- Chlorine (Cl) has an atomic number of 17, meaning it has 17 electrons.
- Its electron configuration is 1s²2s²2p⁶3s²3p⁵.
- Chlorine has seven valence electrons in its outermost shell (3s²3p⁵).
- To achieve an octet, chlorine gains one electron.
- By gaining one electron, chlorine becomes a negatively charged ion (Cl⁻) with a -1 charge.
- This results in the electron configuration becoming 1s²2s²2p⁶3s²3p⁶, which is the same as the noble gas argon (Ar).
The Ionic Bond Formation
When sodium and chlorine are near each other:
- Sodium transfers its single valence electron to chlorine.
- Sodium becomes a Na⁺ ion.
- Chlorine becomes a Cl⁻ ion.
- The positively charged sodium ion (Na⁺) and the negatively charged chloride ion (Cl⁻) are attracted to each other due to their opposite charges.
- This electrostatic attraction forms an ionic bond, creating the compound sodium chloride (NaCl), commonly known as table salt.
In summary, sodium achieves an octet by losing its valence electron, becoming a positively charged ion, while chlorine achieves an octet by gaining an electron, becoming a negatively charged ion. The resulting electrostatic attraction between these ions forms an ionic bond and creates a stable compound.
