Multiple Choice
Which of the following electron configurations represents an atom 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 (atomic number 5)?
A
1s^2 2s^1 2p^1
B
1s^2 2s^1 2p^2
C
1s^2 2s^2 2p^2
D
1s^2 2s^2 2p^1
Verified step by step guidance1
Step 1: Identify the atomic number of boron, 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.
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: $2p^1$. Therefore, the electron configuration is $1s^2 2s^2 2p^1$.
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