C1.2

Question 1

John Dalton (1803)

Answer 1

Daltons theory stated that atoms are indivisible and atoms of a given element are identical. His theory also states that compounds are made from different types of atoms. His model was a solid sphere.

Question 2

J.J Thompson (1904)

Answer 2

Thompson discovered electrons in which he won a noble prize for him. He then created the ‘Plum Pudding Model’ of the atom. This model shows the atom as composed of electrons scattered in a cloud of positive charge.

Question 3

Ernest Rutherford (1911)

Answer 3

Rutherford carried out an experiment where he shot positively charged alpha particles at a thin sheet of gold foil. His results were that most alpha particles passed through the gold sheet of foil but some particles deflected. This was only possible if the atom was mostly empty.

Question 4

Niels Bohr (1913)

Answer 4

Bohr modified Rutherford’s model of the atom. He stated that electrons move around the nucleus in orbits of fixed sized. In this model electrons could not occupy values of energy between the fixed energy levels. This model was the planetary model.