Multiple Choice
Which of the following is the ground state electron configuration for a Ca^{2+} ion?
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10. Periodic Properties of the Elements
The Electron Configuration: Ions
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Which of the following is the correct electron configuration for the chloride ion, Cl⁻?
A
1s^2 2s^2 2p^6 3s^2 3p^3
B
1s^2 2s^2 2p^6 3s^2 3p^5
C
1s^2 2s^2 2p^6 3s^2 3p^6
D
1s^2 2s^2 2p^6 3s^2 3p^4
Verified step by step guidance1
Identify the atomic number of chlorine (Cl), which is 17. This means a neutral chlorine atom has 17 electrons.
Understand that the chloride ion (Cl⁻) has gained one extra electron compared to the neutral atom, so it has 18 electrons in total.
Recall the order of filling electron orbitals according to the Aufbau principle: 1s, 2s, 2p, 3s, then 3p.
Write the electron configuration for 18 electrons by filling orbitals in order: 1s^2, 2s^2, 2p^6, 3s^2, and 3p^6.
Compare the given options to this configuration and select the one that matches the full 18-electron configuration for Cl⁻.
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