Sodium (Na) before reaction:
* Electron configuration: 1s² 2s² 2p⁶ 3s¹
* Valence shell: 3s¹ (contains 1 electron)
Sodium (Na) after reaction (in NaCl):
* Electron configuration: 1s² 2s² 2p⁶
* Valence shell: 2p⁶ (contains 8 electrons)
Explanation:
* Sodium is in Group 1 of the periodic table, meaning it has one valence electron (in its 3s orbital).
* Chlorine is in Group 17, meaning it has seven valence electrons.
* When sodium reacts with chlorine, sodium *loses* its valence electron to become a positively charged ion (Na⁺).
* Chlorine *gains* this electron to become a negatively charged ion (Cl⁻).
* This transfer of electrons creates an ionic bond, forming the compound NaCl.
Therefore, sodium has 1 valence electron before reacting with chlorine and 8 valence electrons after reacting with chlorine. This is because it has lost its single valence electron and now has a full outer shell.
