Multiple Choice
Which of the following is the correct electron configuration for the chloride ion, Cl⁻?
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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 phosphorus (atomic number 15)?
A
1s^2 2s^2 2p^6 3s^2 3p^1
B
1s^2 2s^2 2p^6 3s^2 3p^6
C
1s^2 2s^2 2p^6 3s^2 3p^3
D
1s^2 2s^2 2p^6 3s^2 3p^5
Verified step by step guidance1
Step 1: Identify the atomic number of phosphorus, which is 15. This means phosphorus has 15 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 number of electrons: s orbitals hold 2, p orbitals hold 6.
Step 3: Begin filling the orbitals with electrons: fill 1s with 2 electrons, 2s with 2 electrons, 2p with 6 electrons, and 3s with 2 electrons. This accounts for 12 electrons so far.
Step 4: Place the remaining 3 electrons in the 3p orbital, since phosphorus has 15 electrons total. This gives 3 electrons in 3p.
Step 5: Write the full electron configuration as $1s^{2} 2s^{2} 2p^{6} 3s^{2} 3p^{3}$, which correctly represents the distribution of 15 electrons in phosphorus.
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