Multiple Choice
The innermost electron shell of an atom can hold up to how many electrons?
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10. Periodic Properties of the Elements
The Electron Configuration
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Which of the following is the correct ground-state electron configuration for rubidium (Rb)?
A
1s^2 2s^2 2p^6 3s^2 3p^6 4s^2 3d^{10} 4p^6 5p^1
B
1s^2 2s^2 2p^6 3s^2 3p^6 4s^2 3d^{10} 4p^6 4d^1
C
1s^2 2s^2 2p^6 3s^2 3p^6 4s^2 3d^{10} 4p^6 4s^1
D
1s^2 2s^2 2p^6 3s^2 3p^6 4s^2 3d^{10} 4p^6 5s^1
Verified step by step guidance1
Identify the atomic number of rubidium (Rb), which is 37. This means rubidium has 37 electrons in its neutral ground state.
Recall the order of filling electron orbitals according to the Aufbau principle, which generally follows the sequence: 1s, 2s, 2p, 3s, 3p, 4s, 3d, 4p, 5s, and so on.
Write the electron configuration by filling orbitals in order until you reach 37 electrons. This involves filling up to the 4p orbital completely, which accounts for 36 electrons, and then placing the 37th electron in the next available orbital.
Recognize that after the 4p orbital is filled, the next electron enters the 5s orbital, not the 5p, 4d, or 4s orbitals again, because of the energy levels and the Aufbau principle.
Compare the given options with the correct sequence and identify the configuration that ends with 5s^1, which corresponds to the ground-state electron configuration of rubidium.
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