Multiple Choice
What do electrons in the same shell have in common?
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10. Periodic Properties of the Elements
The Electron Configuration
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What is the electron configuration of the chloride ion (Cl⁻) after a chlorine atom gains an electron?
A
[Ne] 3s² 3p⁶
B
[He] 2s² 2p⁶
C
[Ar] 4s² 3d¹⁰
D
[Ne] 3s² 3p⁵
Verified step by step guidance1
Start by identifying the atomic number of chlorine (Cl), which is 17. This means a neutral chlorine atom has 17 electrons.
Write the electron configuration for a neutral chlorine atom. The configuration is: 1s² 2s² 2p⁶ 3s² 3p⁵. This can be simplified using noble gas notation as [Ne] 3s² 3p⁵.
When chlorine gains an electron to become a chloride ion (Cl⁻), it will have one additional electron, making a total of 18 electrons.
Add the extra electron to the 3p orbital, which can hold up to 6 electrons. The new electron configuration for Cl⁻ becomes: 1s² 2s² 2p⁶ 3s² 3p⁶.
Express the electron configuration of the chloride ion using noble gas notation. Since the configuration is now complete for the third energy level, it can be written as [Ar].
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