Question

as you move down a group, atomic radius increases because - you add more and more shells (energy levels) you add more and more protons you add more atomic mass you add more and more neutrons

Explanation:

To determine why atomic radius increases down a group, we analyze each option:

• Option 1: As you move down a group in the periodic table, each subsequent element has an additional electron shell (energy level). These shells are further from the nucleus, increasing the atomic radius.
• Option 2: Adding more protons (which happens across a period, increasing nuclear charge and decreasing radius) doesn't explain the increase down a group.
• Option 3: Atomic mass increase is related to protons and neutrons, but it's not the direct cause of atomic radius increase down a group.
• Option 4: Adding neutrons affects mass, not the size of the electron cloud (atomic radius) in the way that shell addition does.

So the correct reason is adding more shells (energy levels).

Answer:

A. you add more and more shells (energy levels)