daltons postulants + model and timeline.

Postulant I)

each element is composed of extremely small particles called atoms

Postulant II)

all atoms of a given element are identical, but the atoms of one element are different than the atoms of other elements

III)

atoms of one element cannot be changed into atoms of a different element by chemical reactions; atoms can neother be created nor destroyed.

Postulant IV)

compounds are formed when atoms of more than one element combine; a given compound always has the same relative number and kind of atoms.

1st experiment

J.J. Thompson discovers the electrons using cathode rays by ray being bent. Discovered the combined charge/mass ratio of an electron.

2nd experiment

Millikan’s oil drop experiment had oil dropping between electrically charged plates. Was able to determine the separate charge of the electron and its mass.

Plum Pudding Model

1904; Uniform dense matter with negative electrons distributed randomly throughout.

3rd experiment

Rutherfords Gold Experiment - demonstrated that the atom is mostly empty space with a dense, positively charged center called a nucleus. Was seen after particles bounced off at different angles, some went through as well.