Multiple Choice
A neutral atom has the following electron configuration: 1s^2 2s^2 2p^6 3s^2 3p^5. Which element is this atom?
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10. Periodic Properties of the Elements
The Electron Configuration
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Which of the following represents the correct ground-state electron configuration for the Mn^{2+} ion?
A
1s^2 2s^2 2p^6 3s^2 3p^6 3d^4
B
1s^2 2s^2 2p^6 3s^2 3p^6 3d^3 4s^2
C
1s^2 2s^2 2p^6 3s^2 3p^6 3d^6
D
1s^2 2s^2 2p^6 3s^2 3p^6 3d^5
Verified step by step guidance1
Identify the atomic number of manganese (Mn), which is 25, meaning a neutral Mn atom has 25 electrons.
Write the ground-state electron configuration for neutral Mn: $1s^2 2s^2 2p^6 3s^2 3p^6 4s^2 3d^5$.
Recognize that the Mn$^{2+}$ ion has lost 2 electrons compared to the neutral atom, so it has 23 electrons.
Recall that when transition metals form cations, electrons are removed first from the outermost s orbital (4s) before the d orbitals.
Remove 2 electrons from the 4s orbital of the neutral Mn configuration, resulting in the Mn$^{2+}$ configuration: $1s^2 2s^2 2p^6 3s^2 3p^6 3d^5$.
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