Question:
What is the atomic number of an element having \(ns^1\) electronic configuration and belonging to 3d transition series?
What is the atomic number of an element having \(ns^1\) electronic configuration and belonging to 3d transition series?
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Chromium and copper have \(4s^1\) because of the extra stability of half-filled and full d subshells.
Updated On: Oct 1, 2026
- Only 24
- Only 25
- Only 29
- 24 and 29
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Verified By Collegedunia
The Correct Option is D
Solution and Explanation
Step 1: Understanding the Concept:
Most 3d elements have \(4s^2\), but two elements take one electron from \(4s\) to give a half-filled or completely filled \(3d\) subshell, which is more stable.
Step 2: The two cases:
Chromium (\(Z = 24\)): \(3d^54s^1\), a half-filled d subshell.
Copper (\(Z = 29\)): \(3d^{10}4s^1\), a fully filled d subshell.
Step 3: Conclusion:
Mn (\(Z = 25\)) is \(3d^54s^2\), so it does not have \(ns^1\). Therefore the atomic numbers are \(24\) and \(29\).
Final Answer:
The atomic numbers are \(24\) and \(29\), option (D). \[ \boxed{24\ \text{and}\ 29} \]
Most 3d elements have \(4s^2\), but two elements take one electron from \(4s\) to give a half-filled or completely filled \(3d\) subshell, which is more stable.
Step 2: The two cases:
Chromium (\(Z = 24\)): \(3d^54s^1\), a half-filled d subshell.
Copper (\(Z = 29\)): \(3d^{10}4s^1\), a fully filled d subshell.
Step 3: Conclusion:
Mn (\(Z = 25\)) is \(3d^54s^2\), so it does not have \(ns^1\). Therefore the atomic numbers are \(24\) and \(29\).
Final Answer:
The atomic numbers are \(24\) and \(29\), option (D). \[ \boxed{24\ \text{and}\ 29} \]
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