Question detail
What is the trend in atomic radius across Period 3 of the periodic table?
Try the question, check the answer, then read the explanation to understand the curriculum point.
At a glance
MCQ
Type
practice
Style
Topic
Periodicity
Question
- A. Atomic radius increases from sodium to argon
- B. Atomic radius decreases from sodium to argon
- C. Atomic radius remains constant across Period 3
- D. Atomic radius first increases then decreases across Period 3
Answer
Atomic radius decreases from sodium to argon
Explanation
The atomic radius decreases across Period 3 due to increasing nuclear charge, which pulls the electrons closer to the nucleus. This is supported by periodic data showing that as you move from sodium to argon, the atomic number increases, leading to a stronger attraction between the nucleus and the electron cloud, resulting in a smaller atomic radius.
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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