Protons are particles found in the area known as the atom’s nucleus, which concentrates almost all the atom’s mass. Being found in the atom’s centre or nucleus, protons and neutrons are also known as nucleons. A proton has a positive charge and is one of two types of particles that possess a greater amount of mass in an atom than electrons. The following table lists some of a proton’s characteristics:
| Particle | Mass in kilograms | Electrical charge in coulombs | Location |
| Proton | \(1.67 \cdot 10^{-27}\) | \(1.6022 \cdot 10^{-19}\) | Nucleus |
Figure 1. Protons are found in the atom’s nucleus, which concentrates almost all the mass of its elements.
Proton number
To determine the number of protons in an atom defined by the letter Z, you need to read its nuclide notation. This specifies the number of protons in the lower-left corner of the element symbol.
\(^{12}_{6}C\)
This is a carbon atom. The number of protons in the nucleus is 6.
\(^{16}_{8}O\)
This is an oxygen atom. The number of protons in the nucleus is 8.
The proton number does not change between isotopes.
Protons and the atom’s mass
Protons are one of two types of particles responsible for most of an atom’s mass. The more protons an atom has, the heavier it is. Protons have a mass that is almost 1836.15 times larger than that of electrons and nearly equal to that of neutrons (there is a difference of approximately 0.1%).
Protons and the atom’s charge
Protons are responsible for the positive charge of an atom. An atom’s electrical charge is negative if the number of electrons is larger than the number of protons. Conversely, it is positive if the number of protons exceeds of the number of electrons.
Examples of how protons and electrons determine an atom’s electrical charge are given below:
An oxygen cation lacking two electrons
In this case, the oxygen is not neutral but has an excess of two protons. The total charge is \(1.6022 \cdot 10^{-19}\) coulombs multiplied by two.
An iron cation lacking one electron
In this case, the iron is not neutral but has an excess of one proton, so the total charge is \(1.6022 \cdot 10^{-19}\) coulombs.
Protons and the atom’s relative charge
When thinking about atomic charges, it helps to work with the concept of relative charge. If the electron and the proton have an electrical charge that is equal, then to calculate the total charge, you only need to multiply the atom’s relative charge by the charge of the proton.
\(\text{Total charge} = \text{relative charge of the atom} \cdot \text{charge of a proton}\)
See the following examples of applying relative charges:
A carbon cation with a relative charge of +1
In this case, the carbon is no longer neutral, as it has one extra proton. Its total charge is \(1.6022 \cdot 10^{-19}\) coulombs multiplied by one.
An alpha particle consisting of a helium nucleus without electrons and a relative charge of +2
In this case, the helium is no longer neutral but has an excess of two protons. Its total charge is \(1.6022 \cdot 10^{-19}\) coulombs multiplied by two.
Figure 2. Left, the relative charge of a helium atom. Right, the nucleus of a helium atom, also known as an alpha particle. The relative charges vary, depending on the number of electrons.
Protons - Key takeaways
- Protons are one of two particles adding a greater amount of mass to an atom.
- Protons are almost 1836.15 times heavier than electrons.
- Protons and neutrons have similar masses.
- The number of protons and the lack of electrons determine an atom’s positive charge.
- An atom with an excess of protons is called a cation.
- An atom with an excess of electrons is called an anion.
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