Multiple Choice
Which group in the periodic table contains elements with the smallest atomic radius?
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10. Periodic Properties of the Elements
Periodic Trend: Atomic Radius
Multiple Choice
Given the elements Li, Na, and K, rank them in order of increasing atomic radius.
A
Na < K < Li
B
Na < Li < K
C
K < Na < Li
D
Li < Na < K
Verified step by step guidance1
Recall that atomic radius generally increases as you move down a group (column) in the periodic table because each successive element has an additional electron shell, making the atom larger.
Identify the group to which Li, Na, and K belong. All three elements are in Group 1 (alkali metals), so their atomic radius trend will follow the group trend.
Compare the positions of Li, Na, and K in the periodic table: Li is in period 2, Na is in period 3, and K is in period 4, meaning K has the most electron shells, followed by Na, then Li.
Conclude that the atomic radius increases from Li to Na to K because the number of electron shells increases, which outweighs the effect of increasing nuclear charge in this group.
Therefore, the correct order of increasing atomic radius is: Li < Na < K.
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