An Element

Electrons

Mass:

1/2000

Charge:

-1

Nucleus

Neutrons

Mass:

1

Charge:

0

Protons

Mass:

1

Charge:

+1

Combine with other atoms to form

Molecues

Containing same kind of atoms

Molecules of elements

Examples:

Chlorine gas

Oxygen gas

Containing different kind of atoms

Molecules of compounds

Examples:

CO2

Cl2