Parts of the Atom: Properties  Protons: –Positive charge –Located in nucleus –Mass = 1 amu (Atomic Mass Unit)  Neutrons –No charge (neutral) –Inside nucleus –Mass = 1 amu  Protons and neutrons form the nucleus

Parts of the Atom: Properties  Electrons: –Negative charge –Located in clouds outside the nucleus –Very little mass (1/1800 of proton)  Basic atom: hydrogen –1 proton –1 electron

Parts of the Atom: Properties  Building larger atoms: Neutrons needed –Separates the protons (similar charges repel). –May not be the same number as protons –Atoms of same element may have different number of neutrons. (isotopes)  Atomic number determines identity –The number of protons = atomic number

Parts of the Atom: Properties  Mass number: The mass number is the total number of protons and neutrons in an atom. –Can tell between isotopes by difference in mass  Atomic mass: an weighted average of the masses of different isotopes