Atomic Structure

An atom is made up of subatomic particles: protons (+), electrons (-), and neutrons (n).
- Protons: they are positive and located in the nucleus
- Neutrons: they are neutral and located in the nucleus
- Electrons: they are negative and are located outside the nucleus.



The atomic number is the number of protons in an atom.

Isotopes are different types of atoms of the same chemical element, each having different number of neutrons. Therefore, changing the number of neutrons changes the isotope of the element. All isotopes have the same chemical properties.

The mass number is the total of protons and neutrons. The symbol given is A. Different isotopes also have different masses.

Keep in mind that mass number equals the total number of protons and neutrons

A = atomic # + # of neutrons

-- Jael Lumba