Multiple Choice
Which of the following is the correct electron configuration for aluminum (Al)?
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10. Periodic Properties of the Elements
The Electron Configuration
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Yttrium has an atomic number of 39. Which electron configuration best represents yttrium?
A
1s^2 2s^2 2p^6 3s^2 3p^6 4s^2 3d^{10} 4p^6 5s^2 4d^1
B
1s^2 2s^2 2p^6 3s^2 3p^6 4s^2 3d^{10} 4p^6 5s^2 4d^2
C
1s^2 2s^2 2p^6 3s^2 3p^6 4s^2 3d^{10} 4p^6 5s^1 4d^2
D
1s^2 2s^2 2p^6 3s^2 3p^6 4s^2 3d^{10} 4p^6 4d^2 5s^1
Verified step by step guidance1
Identify the atomic number of yttrium, which is 39. This means yttrium has 39 electrons to be placed in orbitals according to the Aufbau principle.
Recall the order of orbital filling based on increasing energy levels: 1s, 2s, 2p, 3s, 3p, 4s, 3d, 4p, 5s, 4d, and so on.
Fill the orbitals in order, making sure to follow the maximum electron capacity for each: s orbitals hold 2 electrons, p orbitals hold 6, and d orbitals hold 10.
After filling up to 4p^6 (which accounts for 36 electrons), place the remaining 3 electrons in the 5s and 4d orbitals. According to the Aufbau principle, 5s fills before 4d.
Determine the correct electron configuration by placing 2 electrons in 5s and 1 electron in 4d, resulting in the configuration: $1s^2 2s^2 2p^6 3s^2 3p^6 4s^2 3d^{10} 4p^6 5s^2 4d^1$.
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