Atomic StructureTopic 3

HistoryJohn Dalton

Hard sphere modelEarliest modelNo internal structure

JJ ThompsonPlumb Pudding model+ and – charges in nucleusSupported existence of negative particles

Earnest RutherfordEmpty space modelSmall dense nucleusElectrons revolve around nucleus

Bohr’ modelElectrons in specific orbitsOrbits have fixed energyElectron shells

Many scientistsWave mechanical (electron cloud)Electrons in orbitalOrbital – area an electron is likely to be found

Atomic StructureAtom – basic unit of matter

Mostly empty space

Composed of much smaller particles Protons (+)

in nucleus mass = 1 amu Atomic number

Neutrons (o) In nucleus Mass = 1 amu Atomic mass – atomic number = number of neutrons

Electrons (-) In orbitals Mass = 1/2000 of proton [1/1836] In a neutral atom = same as number of protons

Nucleus Small, denseMass of atom (neutron plus protons)Contains protons and neutrons (nucleons) Nuclear charge is (+) contains protons

Mass number Identifies isotopes of the same elementneutrons plus protonsTotal number of nucleons