Question detail
What is the reason for the increase in first ionisation energy 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. Decrease in atomic radius.
- B. Increase in atomic radius.
- C. Increase in electron shielding.
- D. Decrease in nuclear charge.
Answer
Decrease in atomic radius.
Explanation
The increase in first ionisation energy across Period 3 is due to the decrease in atomic radius, which results in a stronger attraction between the nucleus and the outermost electrons, making them harder to remove.
Common mistake
Misunderstanding Ionisation Energy Trends
Students often confuse the trend in first ionisation energy across Period 3 with atomic radius, thinking that ionisation energy decreases as atomic radius increases.
To clarify, remember that first ionisation energy increases across Period 3 due to increased nuclear charge attracting electrons more strongly. Use the formula for ionisation energy trends: as atomic number increases, ionisation energy increases because of greater effective nuclear charge. Therefore, the correct trend is that first ionisation energy increases across Period 3.
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