7amu
Explanation:
Atoms are composed of three particles. Â The proton, neutron, and electron. Â
The mass of the atom in amu is just the number of protons and neutrons in the nucleolus since they both have a mass of about 1 amu. Â Electrons are not counted since they have an incredibly small mass that ultimately does not matter. Â
This atom has 3 protons (positively charged particle) and 4 neutrons (particle with no charge) which together gives a mass of 7 amu.