Question detail
Justify the trend in first ionisation energy across Period 3 elements using periodic data and electronic structure.
Try the question, check the answer, then read the explanation to understand the curriculum point.
At a glance
Question
Type
exam_style
Style
Topic
Periodicity
Question
Justify the trend in first ionisation energy across Period 3 elements using periodic data and electronic structure.
Answer
First ionisation energy increases from sodium to chlorine because the effective nuclear charge felt by the outermost electrons rises across the period, making it harder to remove an electron. Additionally, the electrons are in the same principal energy level, so the increased attraction outweighs the shielding effect, resulting in higher ionisation energies.
Explanation
The answer requires applying periodic data (proton number, effective nuclear charge) and electronic configuration to explain a trend, testing the ability to justify explanations of trends with evidence.
Common mistake
Misinterpreting Periodic Trends
Students often confuse the trends in atomic radius and ionisation energy across Period 3, thinking they behave similarly.
To fix this, students should focus on the underlying reasons for each trend, such as electron shielding and effective nuclear charge, which influence atomic radius and ionisation energy differently.
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