Question detail
Using the periodic data for the elements in Period 3, explain why the atomic radius decreases from sodium to chlorine.
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
Using the periodic data for the elements in Period 3, explain why the atomic radius decreases from sodium to chlorine.
Answer
The atomic radius decreases because the number of protons in the nucleus increases across the period, pulling the electron cloud closer to the nucleus while the electrons are added to the same principal energy level. This increased nuclear charge reduces the size of the electron cloud, leading to a smaller atomic radius.
Explanation
The answer demonstrates understanding of how proton number influences atomic radius across a period, linking periodic data to electronic structure. It tests the ability to justify a trend using quantitative periodic information.
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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