Question detail
How does the first ionisation energy change across Period 3?
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. It decreases from sodium to argon
- B. It increases from sodium to argon
- C. It remains the same across Period 3
- D. It fluctuates without a clear trend
Answer
It increases from sodium to argon
Explanation
The first ionisation energy increases across Period 3 due to the increasing nuclear charge, which makes it more difficult to remove an electron. This trend is evidenced by ionisation energy values that show a consistent increase from sodium to argon, reflecting the greater attraction between the nucleus and the outer electrons.
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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