How can I find the number of neutrons in an atom?

Knowing some basic information about the sub-atomic particles that make up an atom will help you determine the number of neutrons in different situations:

1. Protons have a positive charge, and have a mass of approximately 1 amu and are found in the nucleus.

2. Neutrons are electrically neutral, and have a mass of approximately 1 amu and are found in the nucleus.

3. Electrons have a negative charge, and have a mass of approximately 0 amu and are found outside the nucleus.

4. The atomic number of an atom is determined by its number of protons.

5. A neutral atom has the same number of protons as electrons.

Here are some ways to determine the number of neutrons in an atom, depending on the data you already have:

• (mass number) - (number of protons) = (number of neutrons)


• if neutral, (mass number) - (number of electrons) = (number of neutrons)


• If you know the element name or symbol and its mass, such as carbon-14, find the atomic number on the periodic table and subtract it from the mass.