Multiple Choice
Which of the following best describes the trend in atomic radius as you move down a group on the periodic table, and what is the primary cause of this trend?
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10. Periodic Properties of the Elements
Periodic Trend: Atomic Radius
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Which element is expected to have the largest atomic radius according to periodic trends?
A
He (Helium)
B
Cs (Cesium)
C
F (Fluorine)
D
Fr (Francium)
Verified step by step guidance1
Recall that atomic radius generally increases as you move down a group (column) in the periodic table because additional electron shells are added, increasing the size of the electron cloud.
Also remember that atomic radius decreases as you move from left to right across a period (row) due to increasing nuclear charge pulling electrons closer to the nucleus.
Identify the positions of the given elements: He (top right corner, period 1, group 18), Cs (group 1, period 6), F (group 17, period 2), and Fr (group 1, period 7).
Compare the elements by their group and period: Francium (Fr) is below Cesium (Cs) in group 1, so it has more electron shells and a larger atomic radius than Cs; both are larger than F and He, which are higher up and/or further right.
Conclude that Francium (Fr), being the lowest and furthest left among the options, has the largest atomic radius according to periodic trends.
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