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How to Calculate the Number of Protons, Neutrons and Electrons in Elements

Atoms make up every object you'll ever touch. Those atoms are composed of atomic particles -- a central core of protons and neutrons surrounded by a cloud of electrons. The properties of atoms are determined by the exact configuration of those particles. Change the number of protons and electrons and you change the atom. Change the number of neutrons and you create an isotope. Luckily, the periodic table helps you keep track of how many atomic particles are in each element.

Things You'll Need

Periodic table

Instructions

- 1
  Find an element on the periodic table. The elements in the periodic table are placed in order of increasing atomic number, and the atomic number is the number of protons. For example, nickel has an atomic number of 28, so it has 28 protons.
- 2
  Set the number of electrons equal to the number of protons. Atoms are normally electrically neutral. This means atoms usually do not have a net electrical charge. Protons are positively charged and electrons are negatively charged. To be neutral, an atom must have the same number of electrons as it has of protons. Nickel has the same number of electrons as protons -- 28.
- 3
  Subtract the number of protons from the atomic weight of the element. The atomic weight is also found on the periodic table. The atomic mass is very rarely a whole number, so round the atomic mass to the nearest whole number -- that's called the atomic mass number. That is the total number of particles in the nucleus; that is, it's the number of protons and neutrons. So the number of neutrons is the atomic mass number less the number of protons. Nickel, for example, has an atomic mass of 58.69, which rounds to 59. The number of neutrons is (59 - 28) which is 31 neutrons.

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