1. You have learn in chemistry that in an atom, electrons move around a central core called the nucleus.
2. The nucleus consists of protons and neutrons. It containing almost all the mass of the atom.
3. The nucleus of an atom is very small compared to the size of the atom
4. Protons and neutrons also known as nucleons.

Nuclide Notation

1. Proton number is defined as the number of protons in a nucleus.
2. Nucleon number is defined as the total number of protons and neutrons in a nucleus. It is also known as mass number.
3. A nuclide is a type of atom with a particular proton and nucleon number.
4. A nuclide can be represented by a nuclide notation that shows the symbol of element, proton number and nucleon number.
5. Figure below shows the nuclide notation of a nitrogen.