A tiny dense centre
Rutherford's nuclear model.
Reading the gold foil result
In the gold foil experiment most alpha particles went straight through the foil. A few bounced back.
What should this mean for the atom?
What this lesson covers
The idea
Most of an atom is empty space; all its positive charge and most of its mass are concentrated in a tiny, dense central nucleus, around which electrons revolve like planets (planetary model).
Reading the gold foil result
In the gold foil experiment most alpha particles went straight through the foil. A few bounced back.
What should this mean for the atom?
- Most of it is empty space, with a tiny dense centre
- It is filled evenly with positive pudding
- It is a hard ball with no space at all
Rutherford's conclusions
Open each tab.
Rutherford's picture
The atom is mostly empty. Its positive charge and most of its mass sit in a tiny nucleus. The electrons move around it.
Rutherford's model: most of an atom is empty space; all its positive charge and most of its mass are concentrated in a tiny, dense central nucleus, around which electrons revolve like planets (the planetary model).
Notes
Rutherford's model: mostly empty space, with a tiny, dense, positive nucleus holding most of the mass, and electrons revolving around it like planets.
Check yourself
Why did Rutherford say that most of an atom is empty space?
Where are the positive charge and most of the mass of an atom?
Why is Rutherford's model called the planetary model?
A few alpha particles bounced back. This points to …
- All the alpha particles bounced back. Only a few bounced back.
- Electrons are spread all through the atom. That is Thomson's picture, which could not explain the experiment.
- Most alpha particles passed through the gold foil without deflection — correct. Yes!
- In the nucleus — correct. Yes!
- In the revolving electrons. Electrons carry negative charge and are very light.
- Spread evenly through the atom. That is Thomson's model, which Rutherford's result did not support.
- The nucleus is as large as a planet. The nucleus is extremely small compared with the atom.
- Electrons revolve around the nucleus like planets orbiting the Sun — correct. Yes!
- The electrons sit still inside the nucleus. In this model the electrons revolve around the nucleus, outside it.
- positive charge spread evenly through the atom. Evenly spread charge would only deflect alpha particles slightly.
- an atom that is solid all through. Most alpha particles went straight through, so the atom is mostly empty space.
- a small dense centre with positive charge — correct. Yes!