Nucleon, Proton Numbers, Isotope

Nucleon and Proton Numbers

The nucleon number, also known as the mass number, is the total number of protons and neutrons in the nucleus of an atom.
The proton number, also referred to as atomic number, is the number of protons in the nucleus of an atom.
The proton number uniquely identifies a chemical element.
Changing the number of neutrons does not change the element, but does change the mass number.
Atoms of the same element that have different numbers of neutrons (and therefore different nucleon numbers) are called isotopes.

Isotopes

Isotopes have same proton number but different nucleon numbers.
Physical properties may vary between isotopes, including density, melting point and boiling point.
The chemical properties of isotopes are largely the same because they have the same number of protons and electrons.
Some isotopes are radioactive, meaning they can emit radiation. This property does not depend on the chemical compound the isotope is in.
A radioactive isotope can be used as a tracer in medical or industrial applications, among others.

Remember that understanding the structure of the atom is crucial to studying types of radiation. When isotopes decay, they emit varying types of radiation, changing into different elements in the process.