Mass number, atomic number, ions & isotopes

Electrons

In an atom the number of electrons is equal to the number of protons in the nucleus. This is because atoms have no overall electrical charge so the negative charges on the electrons cancel out the positive charges on the protons.

[[What is the atomic number?[[

The total number of protons inside the atom

[[.What is the mass number?[[

The total number of protons + neutrons inside the atom.

Atoms can be represented as shown in this example:

==Isotopes==

Atoms turn into positive ions if they lose one or more outer electron(s).