Effective Nuclear Charge
Effective nuclear charge (Zeff) experienced by valence electrons:
Select the correct option:
Solution
Increases across a period
Effective Nuclear Charge (Zeff) is the actual net positive charge experienced by an electron in a multi-electron atom.
- Across a period (left to right), the number of protons (atomic number Z) increases by one at each step.
- Simultaneously, electrons are added to the same valence shell.
- Since the shielding provided by electrons in the same shell is not perfect, the gain in Z outweighs the gain in shielding (σ).
- Result: Zeff increases across a period, pulling electrons tighter and reducing atomic radius.
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About This Question
- Subject
- chemistry
- Chapter
- classification of elements and periodicity in properties
- Topic
- effective nuclear charge
- Difficulty
- Medium
- Year
- 2025
Solution
Correct Answer:
Increases across a period
Effective Nuclear Charge (Zeff) is the actual net positive charge experienced by an electron in a multi-electron atom.
- Across a period (left to right), the number of protons (atomic number Z) increases by one at each step.
- Simultaneously, electrons are added to the same valence shell.
- Since the shielding provided by electrons in the same shell is not perfect, the gain in Z outweighs the gain in shielding (σ).
- Result: Zeff increases across a period, pulling electrons tighter and reducing atomic radius.
This medium difficulty chemistry question is from the chapter classification of elements and periodicity in properties, covering the topic of effective nuclear charge. It appeared in the 2025 exam.
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