Atomic And Ionic Radii
Which of the following ions has the largest ionic radius?
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About This Question
- Subject
- chemistry
- Chapter
- classification of elements and periodicity in properties
- Topic
- atomic and ionic radii
- Difficulty
- Medium
- Year
- 2025
Solution
Correct Answer:
O²⁻
All the given species (O2−,F−,Na+,Mg2+) are isoelectronic, meaning they all have 10 electrons.
- For isoelectronic species, the ionic radius is inversely proportional to the atomic number (Z) (nuclear charge).
- O2− (Z=8): 8 protons pull 10 electrons (Weakest pull → Largest size)
- F− (Z=9): 9 protons pull 10 electrons
- Na+ (Z=11): 11 protons pull 10 electrons
- Mg2+ (Z=12): 12 protons pull 10 electrons (Strongest pull → Smallest size) Trend: O2−>F−>Na+>Mg2+.
This medium difficulty chemistry question is from the chapter classification of elements and periodicity in properties, covering the topic of atomic and ionic radii. It appeared in the 2025 exam.
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