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Effective Atomic Number

Mediumchemistry

The effective atomic number (EAN) of Ni in [Ni(CO)4] is:

Select the correct option:

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About This Question

Subject
chemistry
Chapter
coordination compounds
Topic
effective atomic number
Difficulty
Medium
Year
2025
Tags
EAN RuleCarbonyl18-Electron Concept

Solution

Correct Answer:

Nickel has atomic number 28 and oxidation state 0 in [Ni(CO)4]. Each CO donates 2 electrons, so four CO ligands donate 8 electrons. EAN = 28 + 8 = 36, which matches the noble gas krypton.

This medium difficulty chemistry question is from the chapter coordination compounds, covering the topic of effective atomic number. It appeared in the 2025 exam.

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