what is the correct noble gas configuration of chlorine
The Correct Answer and Explanation is:
Correct Answer:
[Ne] 3s² 3p⁵
Explanation:
Chlorine is a chemical element with the atomic number 17, which means it has 17 electrons when in its neutral state. To write its electron configuration, we need to arrange these electrons into the appropriate energy levels or orbitals.
The complete electron configuration of chlorine is:
1s² 2s² 2p⁶ 3s² 3p⁵
However, when asked for the noble gas configuration, we use the symbol of the noble gas that comes before chlorine in the periodic table to represent the core electrons. In chlorine’s case, that noble gas is neon, which has the electron configuration:
1s² 2s² 2p⁶
This accounts for 10 electrons. The remaining 7 electrons (17 – 10 = 7) are then written as:
3s² 3p⁵
So, the noble gas configuration of chlorine becomes:
[Ne] 3s² 3p⁵
This configuration tells us several things. First, chlorine has its valence electrons in the third energy level (principal quantum number n = 3), specifically in the 3s and 3p orbitals. The 3p orbital has 5 electrons, just one short of being completely filled (which would be 3p⁶). That’s why chlorine is highly reactive—it wants to gain one more electron to achieve a full outer shell, just like a noble gas.
By achieving a full valence shell (octet), chlorine becomes more stable. This is also why chlorine often forms -1 ions (Cl⁻) in chemical reactions, especially when bonding with metals like sodium, forming ionic compounds such as sodium chloride (NaCl).
Using noble gas notation makes electron configurations shorter, easier to read, and focuses attention on the valence electrons, which are most important in chemical bonding and reactivity.
