What do you get when you subtract the atomic number from the atomic mass of an element?

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An atom consists of three main type of particles: protons, neutrons and electrons. Protons and neutrons are present within the nucleus, while electrons are outside it. The number of protons in an atom is also known as the atomic number.

Thus, atomic number = number of protons.

The total number...

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An atom consists of three main type of particles: protons, neutrons and electrons. Protons and neutrons are present within the nucleus, while electrons are outside it. The number of protons in an atom is also known as the atomic number.

Thus, atomic number = number of protons.

The total number of protons and neutrons in an atom is known as the mass number. The atomic mass is the weighted average of mass numbers of all the isotopes. Generally an element will not have isotopes, or one dominant isotope. Thus, we generally consider both mass number and atomic mass to be the same.

Therefore, atomic mass = number of protons + number of neutrons

If we subtract the atomic number from the atomic mass:

atomic mass - atomic number = number of protons + number of neutrons - number of protons.

= number of neutrons

Thus we get the number of neutrons present in an atom when we subtract the atomic number from the atomic mass.

Hope this helps. 

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