Question detail
Explain how the first ionisation energy changes across Period 3 and what this indicates about the atomic structure of these elements.
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At a glance
Question
Type
exam_style
Style
Topic
Atomic structure
Question
Explain how the first ionisation energy changes across Period 3 and what this indicates about the atomic structure of these elements.
Answer
The first ionisation energy increases across Period 3 due to the increasing nuclear charge, which attracts the outer electrons more strongly. This indicates that the atomic radius decreases as the effective nuclear charge increases, making it harder to remove an electron.
Explanation
This answer is strong because it clearly links the trend in ionisation energy to changes in atomic structure, demonstrating an understanding of the relationship between nuclear charge and electron removal. The question tests the student's ability to interpret ionisation energy data and relate it to atomic properties.
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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