Physics Partical Model

Plum Pudding Model

Created by JJ Thompson, the model of the atom consisted of a sphere of positive charge with electrons within

JJ Thompson's Discovery

In the early 20th century JJ Thompson discovered the electron which led him to build the plum pudding model

Earnest Rutherford

Made the alpha particle scattering experiment which allowed him to develop the nuclear model

Alpha Particle Scattering Experiment

In 1910, Rutherford setup an experiment which fired alpha particles into a thin gold foin with detectors surrounding it

Hypothesis of experiment

According to the plum pudding model, the positively charged alpha particles would go straight through or be slightly deflect by the gold foil

Results of experiment

Unexpectedly, although most particles managed to pass through, a large amount were deflected at high angles and some were even reflected --> there has to be a positively charged object inside (nuclues)

Conclusion of Rutherford's experiment

• Most particles pass through mean the atom meant it was mostly empty space

• Nucleus must be positively charged for the alpha particles to reflect/deflect

• Nucleus must be small as little particles were reflected

Rutherford's Nuclear Model

A positive nucleus was in the centre of the atom with a cloud of negative electrons surrounding it

Neils Bohr

Danish scientist who proposed that electrons can only orbit at specific distances - these orbital layers are energy levels or 'shells'

Positron

Antiparticle of an electron - has same mass but a +1 charge - emitted by atom during radioactive decay