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Multiple Choice
Which of the following elements has the smallest atomic radius?
A
Mg
B
Cl
C
Na
D
Al
Verified step by step guidance
1
Recall that atomic radius generally decreases across a period (left to right) on the periodic table due to increasing effective nuclear charge pulling electrons closer to the nucleus.
Identify the period and group of each element: Na (Sodium) is in period 3, group 1; Mg (Magnesium) is in period 3, group 2; Al (Aluminum) is in period 3, group 13; Cl (Chlorine) is in period 3, group 17.
Since all elements are in the same period (period 3), compare their positions from left to right: Na < Mg < Al < Cl in terms of increasing atomic number.
Because atomic radius decreases from left to right across a period, Cl, being the farthest to the right among the given elements, will have the smallest atomic radius.
Therefore, the element with the smallest atomic radius among Na, Mg, Al, and Cl is Cl.