John Dalton (1803)

Atomic Contribution (See back of notes)

1. All matter composed of atoms

2. Atoms of same elements are alike

3. Atoms of different elements are different

4. Cmpds are formed by joining elements in simple ratios

5. In rxns, atoms combine, rearrange but never created nor destroyed

Sketch

Crookes (1870)• Atoms=smallest particle• Used vacuum tube, cathode ray tube, Crookes tube• Must be smaller particles b/c cast shadows in tube.• Sketch

J.J. Thompson(1897)• Used Crookes Tube added magnets noticed particle went towards +

particle must be -, credited with discovering electron(e-)• Sketch Plum Pudding Model

Lord Ernest Rutherford (1909)• Famous Gold Foil Experiment• Nucleus is small dense & + charged• Atom mostly empty space (Empty Space Concept)• Sketch

Rutherford's Experiment Nuclear Atom - YouTube.mht

Niels Bohr (1913)• Orbit=e- travel at fixed distance from nucleus, greater

distance=more e-(energy levels)• Ground state-lowest energy state (stable)• Excited state-unstable jump to highest level than fall emitting energy

(light)• Quanta-light exist as bundles of energy• Sketch

Charge cloud model orbital model Quantum Mechanical Model(1930-present)

• Probable location of e-• Cloud of negative charges• +Nucleus surrounded by – cloud• Sketch

HowStuffWorks Videos "Assignment Discovery: Origin of the Atom ...

Atomic Theory- atoms are the basic building block of all matter

Law of definite proportions- A cmpd always contains the same elements in the same proportion by weight

Law of Conservation of Mass – Mass is not created nor destroyed its rearranged (LaVosier)

Law of Multiple Proportions when 2 elements combine to form 2 or more cmpds the mass of 1 element that combines with the mass of the other is in the ratio of small whole #