Multiple Choice
Which of the following diagrams correctly represents the distribution of electrons in the electron shells of a helium atom?
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10. Periodic Properties of the Elements
The Electron Configuration
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Which of the following electron configurations represents an atom of sulfur (atomic number 16) in an excited state?
A
1s^2 2s^2 2p^6 3s^2 3p^6
B
1s^2 2s^2 2p^6 3s^2 3p^3 4s^1
C
1s^2 2s^2 2p^6 3s^1 3p^5
D
1s^2 2s^2 2p^6 3s^2 3p^4
Verified step by step guidance1
Step 1: Identify the ground-state electron configuration of sulfur (atomic number 16). Sulfur has 16 electrons, so fill the orbitals in order of increasing energy: 1s, 2s, 2p, 3s, and 3p until all 16 electrons are placed. The ground-state configuration is $1\mathrm{s}^2 2\mathrm{s}^2 2\mathrm{p}^6 3\mathrm{s}^2 3\mathrm{p}^4$.
Step 2: Understand what an excited state means. An excited state occurs when one or more electrons have absorbed energy and moved to a higher energy orbital than in the ground state, without changing the total number of electrons.
Step 3: Examine each given electron configuration and check if it has 16 electrons total and if any electron is promoted to a higher energy orbital compared to the ground state.
Step 4: For example, the configuration $1\mathrm{s}^2 2\mathrm{s}^2 2\mathrm{p}^6 3\mathrm{s}^1 3\mathrm{p}^5$ has 16 electrons but shows one electron moved from the 3s orbital to the 3p orbital, indicating an excited state.
Step 5: Confirm that the other configurations either represent the ground state or have incorrect electron counts or distributions, and thus are not excited states of sulfur.
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