Multiple Choice
Which of the following represents the ground-state electron configuration of calcium (atomic number 20)?
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10. Periodic Properties of the Elements
The Electron Configuration
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Which of the following is the ground-state electron configuration of the F⁻ ion?
A
1s^2 2s^2 2p^5
B
1s^2 2s^2 2p^4
C
1s^2 2s^2 2p^6
D
1s^2 2s^2 2p^3
Verified step by step guidance1
Identify the atomic number of fluorine (F), which is 9. This means a neutral fluorine atom has 9 electrons.
Recall that the electron configuration of a neutral fluorine atom is $1s^2 2s^2 2p^5$, corresponding to 9 electrons distributed in the shells.
Understand that the F⁻ ion has gained one extra electron compared to the neutral atom, so it has 10 electrons in total.
Add the extra electron to the 2p subshell, which can hold up to 6 electrons, resulting in the configuration $1s^2 2s^2 2p^6$ for the F⁻ ion.
Conclude that the ground-state electron configuration of the F⁻ ion is $1s^2 2s^2 2p^6$, reflecting a full second shell.
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