Question

the mass of an atom is primarily determined by the mass of its ___.
○ protons
○ neutrons
○ protons and neutrons
○ neither protons nor neutrons

question 10
4 pts
which subatomic particle contributes least to the mass of an atom?
○ proton
○ neutron
○ electron

Explanation:

First Question:

An atom's mass is mainly from protons and neutrons (nucleus), as electrons have negligible mass. So the correct option is protons and neutrons.

Electrons have a much smaller mass (≈1/1836 of a proton/neutron) and contribute the least to an atom's mass.

Answer:

C. protons and neutrons

Second Question: