Question detail
What is the general trend in first ionisation energy down Group 2?
Try the question, check the answer, then read the explanation to understand the curriculum point.
At a glance
MCQ
Type
practice
Style
Topic
Atomic structure
Question
- A. It increases down the group.
- B. It decreases down the group.
- C. It remains constant down the group.
- D. It fluctuates down the group.
Answer
It decreases down the group.
Explanation
First ionisation energy decreases down Group 2 due to increased atomic radius and shielding effect, which reduce the effective nuclear charge felt by the outermost electron.
Common mistake
Misinterpreting ionisation energy trends
Students often think that ionisation energy increases steadily across a period and decreases down a group, ignoring the effect of subshell filling and electron shielding.
Explain that ionisation energy rises across a period due to increasing nuclear charge and decreasing atomic radius, but drops when a new subshell begins (e.g., from Na to Mg). Down a group, ionisation energy decreases because added electrons are farther from the nucleus and more shielded, reducing the energy required to remove an electron.
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