Multiple Choice
How many half-filled orbitals are present in a ground-state bromine (Br) atom?
3
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10. Periodic Properties of the Elements
The Electron Configuration
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Which of the following is the correct electron configuration for aluminum (atomic number 13)?
A
1s^2 2s^2 2p^6 3s^2 3p^3
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^2
Verified step by step guidance1
Step 1: Identify the atomic number of aluminum, which is 13. This means aluminum 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, then 3p.
Step 3: Fill the orbitals with electrons following the maximum capacity of each: 1s can hold 2 electrons, 2s can hold 2, 2p can hold 6, 3s can hold 2, and 3p can hold 6.
Step 4: Distribute the 13 electrons accordingly: fill 1s with 2, 2s with 2, 2p with 6, 3s with 2, and place the remaining electron in 3p.
Step 5: Write the electron configuration as $1s^{2} 2s^{2} 2p^{6} 3s^{2} 3p^{1}$, which correctly accounts for all 13 electrons.
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