Question

which statement is the reason why mg has a smaller atomic radius than na?
mg is a metal and na is a metalloid
mg has more energy levels than na
mg tends to form cations, while na tends to form anions
mg has greater nuclear charge than na

Explanation:

Atomic radius is influenced by nuclear charge. Mg (atomic number 12) has more protons than Na (atomic number 11), resulting in a greater nuclear charge. This stronger attraction pulls the electrons closer, making Mg's atomic radius smaller. Metals and metalloids classification is not related to this size - difference. Mg and Na have the same number of energy levels. Both tend to form cations.

Answer:

Mg has greater nuclear charge than Na.