Question

compared to the size of a sodium atom, a magnesium atom would have
a smaller atomic radiusthe same atomic radiusdouble the atomic radiustriple the atomic radius

Explanation:

Sodium (Na) and magnesium (Mg) are in the same period. As we move across a period from left to right, the number of protons increases while electrons are added to the same energy level. The increased nuclear charge pulls the electrons closer, reducing atomic radius. Mg is to the right of Na, so it has a smaller atomic radius.

Answer:

a smaller atomic radius