Question

3 ccc scale, proportion, and quantity which subatomic particles account for most of an atoms mass and volume?

Explanation:

Protons and neutrons are in the nucleus and have significant mass (about 1 amu each). Electrons have negligible mass. The volume of an atom is mostly empty space where electrons move. The nucleus is very small in volume compared to the whole - atom volume. So, protons and neutrons account for most of an atom's mass, and electrons account for most of an atom's volume (due to their movement in the large electron - cloud).

Answer:

Protons and neutrons account for most of an atom's mass; electrons account for most of an atom's volume.