Multiple Choice
Which of the following electron configurations represents an atom of calcium (atomic number 20) in an excited state?
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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 boron (B)?
A
1s^2 2s^2 2p^1
B
1s^2 2s^1 2p^2
C
1s^2 2s^1 2p^3
D
1s^2 2s^2 2p^3
Verified step by step guidance1
Step 1: Identify the atomic number of boron (B), which is 5. This means boron has 5 electrons to place in its electron configuration.
Step 2: Recall the order in which electron orbitals are filled according to the Aufbau principle: 1s, 2s, then 2p orbitals.
Step 3: Fill the 1s orbital first with 2 electrons: \$1s^2$.
Step 4: Next, fill the 2s orbital with 2 electrons: \$2s^2$.
Step 5: Place the remaining 1 electron in the 2p orbital: \$2p^1\(. Thus, the electron configuration is \)1s^2 2s^2 2p^1$.
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