Multiple Choice
Which of the following is the correct electron configuration for bromine (Br, atomic number 35)?
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10. Periodic Properties of the Elements
The Electron Configuration
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Which of the following represents the correct electron configuration for an aluminum (Al) atom?
A
1s^2 2s^2 2p^6 3s^2 3p^2
B
1s^2 2s^2 2p^6 3s^2 3p^1
C
1s^2 2s^2 2p^6 3s^1 3p^2
D
1s^2 2s^2 2p^6 3s^2 3p^3
Verified step by step guidance1
Step 1: Identify the atomic number of aluminum (Al), which is 13. This means an aluminum atom has 13 electrons to be placed in orbitals according to the Aufbau principle.
Step 2: Recall the order of filling orbitals based on increasing energy: 1s, 2s, 2p, 3s, 3p, etc. Each orbital can hold a specific maximum number of electrons: s (2), p (6), d (10), f (14).
Step 3: Begin filling the orbitals with electrons in order: fill 1s with 2 electrons, 2s with 2 electrons, 2p with 6 electrons, and 3s with 2 electrons. Count the total electrons placed so far.
Step 4: After filling 1s, 2s, 2p, and 3s orbitals, you have placed 2 + 2 + 6 + 2 = 12 electrons. Since aluminum has 13 electrons, place the remaining 1 electron in the next available orbital, which is 3p.
Step 5: Write the full electron configuration for aluminum as $1s^{2} 2s^{2} 2p^{6} 3s^{2} 3p^{1}$, ensuring the total number of electrons sums to 13 and follows the correct filling order.
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