Question:
Which of the following elements has an electronic configuration, \([\text{Ar}]\ 4s^{2}\) ?
Which of the following elements has an electronic configuration, \([\text{Ar}]\ 4s^{2}\) ?
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Add up the electrons: argon has 18 and the 4s subshell holds 2 more.
Updated On: Nov 12, 2026
- \(\text{Na}\)
- \(\text{Mg}\)
- \(\text{K}\)
- \(\text{Ca}\)
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The Correct Option is D
Solution and Explanation
Step 1: Understanding the Concept
The symbol \([\text{Ar}]\) stands for 18 electrons. The extra \(4s^{2}\) adds 2 electrons.
Step 2: Calculation
Total electrons \(= 18 + 2 = 20\), so the atomic number is 20, which is calcium.
Step 3: Result
Calcium is the second element of period 4 and belongs to group 2.
Final Answer:
The element is calcium. \[ \boxed{\text{(D) }\text{Ca}} \]
The symbol \([\text{Ar}]\) stands for 18 electrons. The extra \(4s^{2}\) adds 2 electrons.
Step 2: Calculation
Total electrons \(= 18 + 2 = 20\), so the atomic number is 20, which is calcium.
Step 3: Result
Calcium is the second element of period 4 and belongs to group 2.
Final Answer:
The element is calcium. \[ \boxed{\text{(D) }\text{Ca}} \]
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