Question

The mass of an atom is ________________________.

Answer 1

The mass of an atom primarily depends on its mass number, which is the sum of the protons and neutrons, and is expressed in atomic mass units (amu).

Step-by-step explanation:

The mass of an atom is determined by the number of protons and neutrons it contains, which is known as the mass number (A). Protons and neutrons both have a mass close to one atomic mass unit (amu), which is defined as one-twelfth of the mass of a carbon-12 atom.

An atomic mass unit is approximately 1.67 × 10-27 kilograms. The mass of an atom can be approximated by its mass number, as electrons contribute negligibly to the overall mass. Therefore, the mass in atomic mass units is nearly equal to the sum of the protons and neutrons in the atom (mass number A).

Answer 2

The mass of an atom comes from the protons and neutrons that is found in the nucleus. The number of protons is the atomic number of an element. To find the number of neutrons, subtract the atomic number from the mass of an atom. For example, sodium’s atomic number is 11. This will tell us that sodium has 11 protons in it. The atomic mass of sodium is 23. So subtract 23 form 11 gives us 12. Therefore, there are 12 neutrons in sodium.