Key learning points

1. Protons have a positive electric charge of +1 and a mass number of 1.
2. Neutrons have no electric charge and have a mass number of 1.
3. The atomic number of an element equals the number of protons in the nucleus of each atom of that element.
4. The atomic number of an element equals the number of electrons in each atom of that element.
5. Atoms of an element that have different numbers of neutrons in their nuclei are isotopes of the element.

Keywords

• Nucleus - the central part of an atom which contains protons and neutrons

• Nucleon - the term for particles in a nucleus (protons and neutrons)

• Atomic (proton) number - the number of protons within a particular nucleus

• Mass (nucleon) number - the total number of nucleons within a particular nucleus (protons + neutrons)

• Isotopes - atoms of the same element with differing numbers of neutrons

Common misconception