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How many unpaired electrons are present in \(_{26}Fe^{3+}\)?

Chemistry
WAEC 2023

How many unpaired electrons are present in \(_{26}Fe^{3+}\)?

  • A. 4
  • B. 2
  • C. 3
  • D. 5
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Correct Answer: Option D
Explanation

There are 5 unpaired electrons present in \(_{26}Fe^{3+}\).

The atomic number of iron is 26, so it has 26 electrons. When iron loses 3 electrons to form \(Fe^{3+}\), it loses 2 from the s orbital and 1 from the d orbital. This leaves 5 unpaired electrons in the d orbital.

The electron configuration of \(Fe^{3+}\) is [Ar]3d5. The 5 d electrons are all unpaired because Hund's rule states that electrons will occupy degenerate orbitals singly before they pair up. This is because unpaired electrons have a lower energy than paired electrons.


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WAEC May/June 2024 - Practice for Objective & Theory - From 1988 till date, download app now - 99995
Post-UTME Past Questions - Original materials are available here - Download PDF for your school of choice + 1 year SMS alerts
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Post-UTME Past Questions - Original materials are available here - Download PDF for your school of choice + 1 year SMS alerts
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WAEC May/June 2024 - Practice for Objective & Theory - From 1988 till date, download app now - 99995