Multiple Choice
What is the electron configuration for a neutral calcium atom?
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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^2 2p^2
B
1s^2 2s^2 2p^1
C
1s^2 2s^1 2p^3
D
1s^2 2s^1 2p^2
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: electrons fill orbitals starting from the lowest energy level to higher ones. The order for the first 5 electrons is 1s, then 2s, then 2p.
Step 3: Fill the 1s orbital first, which can hold up to 2 electrons, so write $1s^{2}$.
Step 4: Next, fill the 2s orbital, which can also hold up to 2 electrons, so write $2s^{2}$.
Step 5: Finally, place the remaining electron in the 2p orbital, which can hold up to 6 electrons, so write $2p^{1}$. Combine all to get the electron configuration: $1s^{2} 2s^{2} 2p^{1}$.
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