What is the electron configuration for Cl, chlorine, and how many valence electrons does Cl have?
The correct answer and explanation is:
The electron configuration for chlorine (Cl) is:
1s² 2s² 2p⁶ 3s² 3p⁵
Explanation:
- Atomic Number of Chlorine:
Chlorine has an atomic number of 17, which means it has 17 protons and, in its neutral state, 17 electrons. - Electron Distribution Across Shells:
Electrons occupy atomic orbitals in increasing order of energy (the Aufbau principle). For chlorine:- The first shell (n=1) has 2 electrons in the 1s orbital: 1s².
- The second shell (n=2) has 8 electrons: 2 in the 2s orbital and 6 in the 2p orbitals: 2s² 2p⁶.
- The third shell (n=3) holds the remaining 7 electrons: 2 in the 3s orbital and 5 in the 3p orbitals: 3s² 3p⁵.
- Valence Electrons:
Valence electrons are the outermost electrons that participate in chemical bonding. For chlorine, the valence electrons are those in the third shell: 3s² 3p⁵. This totals 7 valence electrons. - Chemical Behavior of Chlorine:
Chlorine is a halogen, located in Group 17 (7A) of the periodic table. Its 7 valence electrons mean it is one electron short of a full octet, which drives its tendency to gain an electron during chemical reactions. This results in the formation of a chloride ion (Cl⁻) with a stable electron configuration of [Ne] 3s² 3p⁶, equivalent to the noble gas argon. - Significance in Bonding:
Chlorine commonly forms ionic bonds by accepting an electron from a metal (e.g., NaCl) or covalent bonds by sharing electrons with nonmetals (e.g., Cl₂). Its high electronegativity contributes to its strong reactivity.
Understanding chlorine’s electron configuration explains its placement in the periodic table and its reactivity in chemical processes.