Question

Name the particle which determines the mass of an atom.

Answer 1

Atom:

1. An atom is defined as any particle of matter at its most basic level which contains at least one proton.
2. An atom consists of a nucleus that is usually surrounded by one or more electrons.
3. Each electron is negatively charged.
4. The nucleus is charged positively and contains one or more relatively heavy particles known as protons and neutrons.

Particles that determine the mass of an atom:

1. Consider an atom of hydrogen. The hydrogen atom consists of a nucleus, formed of a single proton, and of a single electron.
2. The hydrogen molecule consists of two hydrogen atoms bound together. The molar mass of hydrogen is $2.016\raisebox{1ex}{$g$}\!\left/ \!\raisebox{-1ex}{$mole$}\right.$.
3. As all hydrogen atoms contain exactly one proton. hence its atomic number is about one.
4. The atomic mass of a hydrogen atom is $1.00784amu$
5. The unit of atomic mass is amu (atomic mass unit).
6. An amu (atomic mass unit) is defined as accurately $\raisebox{1ex}{$1$}\!\left/ \!\raisebox{-1ex}{$12$}\right.$ the mass of a carbon$-12$ atom. The carbon$-12$ atom has six neutrons and six protons in its nucleus.
7. Protons and neutrons are responsible mainly for the mass of an atom.
8. As protons and neutrons are so much more massive than electrons.
9. Hence almost all of the mass of an atom comes from the nucleus, which contains all of the neutrons and protons.

Thus, protons and neutrons are the particles that determine the mass of an atom.