Subatomic Particles

After reading this section you will be able to do the following:

  • List the three main subatomic particles of an atom.
  • Discuss the positions of these particles within the atom and what electric charge they carry, if any.

Atom Composition

Now that we have talked the basics of atoms and elements, let's talk about the particles that make up the atom. Particles that are smaller than the atom are called subatomic particles. The three main subatomic particles that form an atom are protons, neutrons, and electrons. The center of the atom is called the nucleus

Protons and Neutrons

Protons and neutrons make up the nucleus of an atom. All protons are identical to each other, and all neutrons are identical to each other. Protons have a positive electrical charge, so they are often represented with the mark of a "+" sign. Neutrons have no electrical charge and are said to help hold the protons together since protons are positively charged particles and should repel each other.

If all protons are identical and all neutrons are identical, then what makes the atoms of two different elements different from each other? For example, what makes a hydrogen atom different from a helium atom? As mentioned in our discussion of elements and the periodic table, the number of protons and neutrons in the nucleus give the atoms their specific characteristics. In the graphic below you will notice that each of the three elements have different numbers of protons (red spheres) and neutrons (blue spheres). 

 This is a diagram of three different atoms and their subatomic particles. The hydrogen atom has one proton and one electron. The helium atom has two protons, two neutrons, and two electrons. The beryllium atom has four protons, four neutrons, and four electrons


As shown in the figure above, electrons surround the nucleus. Electrons are negatively charged subatomic particles that are as negative as protons are positive. In general, atoms like to have the same number of electrons as they have protons in order to be electrically balanced. Electrons also play an important role in how atoms bond to each other to form molecules and will therefore be discussed in more detail in future sections of this module.


  1. Subatomic particles are particles that are smaller than the atom.
  2. Protons, neutrons, and electrons are the three main subatomic particles found in an atom.
  3. Protons have a positive (+) charge. An easy way to remember this is to remember that both proton and positive start with the letter "P."
  4. Neutrons have no electrical charge. An easy way to remember this is to remember that both neutron and no electrical charge start with the letter "N."