Chem 2 - Bonding and Calculations - Atoms, Compounds and Isotopes

Atoms are made up of three small particle:

- Protons (Charge + 1 and Mass 1)

- Neutrons (Charge 0 and Mass 1)

- Electrons (Charge -1 and Mass 1/2000)

There are two numbers that describe an atom: 

- The Mass Number tells you the total number of Neutrons and Protons in the Nucleus of a specific atom

- The Proton Number tells you the total number of Protons in a specific atom. (And as there are the same number of Electrons as Protons in an atom, it tells you the number of Electrons)

Compounds are formed when atoms of two or more elements are Chemically Combined together

Isotopes are different atomic forms of the same element. This difference is the Number of neutrons in the nucleus. There are always the same number of Protons. 

This means they have different Mass Numbers but the same Atomic Numbers. If they had different Atomic Numbers they would be different elements all together.