AQA Triple Science: Physics 6 markerWatch
Scientists sometimes replace one scientific model with a different model.
For example in the early 20th Century the plum pudding model of the atom was
replaced by the nuclear model of the atom.
Explain what led to the plum pudding model of the atom being replaced by the
nuclear model of the atom.
In the early 20th century scientists in Ernest Rutherford's lab conducted the golden foil experiment. This experiment consisted of firing alpha particles at a thin sheet of gold. Most of the particles fired passed straight through, without changing course. This indicated that the majority of the atom is empty space. Some particles though, bounced back or changed course, indicating that the atom had a positive charge in the middle and that the majority of the atom's mass was concentrated in the center. This contradicts the plum pudding model of the atom as in the plum pudding model, the mass and charges are spread throughout the atom. This lead to the replacement of the plum pudding model with the nuclear model of the atom
Here's the model answer:
The Gold Foil experiment that was carried out by Rutherford, Geiger and Mardsen showed that there was something in the atoms of gold that was positively charged and heavy. This was called the nucleus and it was known to have a + charge. this disproved Thomson's model that the positive in the atom was like jelly. The gold foil experiment also showed that most of the atom was empty space - which again disproved Thomson's model because Thomson's model had no empty space. Therefore Rutherford came up with a new model, where the nucleus was in the centre (they didnt know about neutrons at this time) and the electrons were in the space surrounding it. Rutherford's experiment disproved Thomson's model which is why it was replaced.
I'd say 5 marks?