Nucleon
Definition and meaning of Nucleon in chemistry.
A nucleon is a general name for either a proton or a neutron. These heavy subatomic particles pack tightly together to build the central nucleus of an atom. Together, nucleons account for almost the entire mass of every object in the universe.
In more detail
Protons carry a positive electric charge. Neutrons are completely neutral and carry no charge at all. Both of these particles have almost exactly the same weight.
Each one weighs about one atomic mass unit. They are held firmly together in the atomic center by the strong nuclear force. This force is one of the four main forces in nature.
It works like an incredibly strong glue at very short distances. The strong force easily overcomes the natural push of positive protons trying to repel each other. The total count of nucleons in an atom is called the mass number.
This number dictates exactly which isotope of an element you are looking at. For example, a carbon atom always has six protons. If it also has six neutrons, it has a total of twelve nucleons.
If it has seven neutrons, it has a total of thirteen nucleons. Both are still carbon, but they have completely different total weights. Electrons are extremely tiny and orbit far outside the center. They are never considered nucleons.
Key facts
| Particles | Protons and neutrons |
|---|---|
| Location | Strictly inside the atomic nucleus |
| Mass Contribution | More than 99.9 percent of an atom's total weight |
| Binding Energy | Held together by the strong nuclear force |
| Mass Number | Equals the total count of nucleons |
An oxygen-16 atom has a mass number of 16. This means its nucleus contains exactly 16 total nucleons. Since oxygen always has 8 protons, the remaining 8 particles must be neutrons. This heavy cluster of 16 particles forms the incredibly dense core of the oxygen atom. To picture this density, imagine packing 16 heavy marbles tightly into the center of a giant football stadium. The marbles are the nucleons, and the stadium is the whole atom.
Frequently asked questions
Is an electron considered a nucleon?
No. Nucleons exist exclusively inside the atomic nucleus. Electrons orbit far outside the nucleus and weigh almost nothing.
Why don't the positive protons push each other apart?
The strong nuclear force acts as a very powerful glue. It is much stronger than the electrical force trying to push the protons apart.
Do protons and neutrons weigh the exact same amount?
They are very close. A neutron is slightly heavier than a proton, but chemists usually treat them both as having a mass of one atomic mass unit.