Why atoms should collapse
Rutherford's model cannot explain stability.
A circling electron
In Rutherford's model, an electron goes round and round the nucleus, like a ball whirled on a string.
What does the model say should happen to a charged electron that keeps circling?
What this lesson covers
The idea
An electron revolving around the nucleus is accelerating and should lose energy, spiral inward and fall into the nucleus, collapsing the atom; since atoms are stable, Rutherford's model is not completely correct.
A circling electron
In Rutherford's model, an electron goes round and round the nucleus, like a ball whirled on a string.
What does the model say should happen to a charged electron that keeps circling?
- It should lose energy and spiral into the nucleus
- It should circle for ever with no change
- It should fly out of the atom
Run the model
Press the button to see what Rutherford's model predicts for the electron.
A problem with the model
A particle moving in a circle keeps changing direction, so it is accelerating (Chapter 4). An accelerating electron should lose energy, spiral inward and fall into the nucleus.
An electron revolving around the nucleus is accelerating and should lose energy, spiral inward and fall into the nucleus, collapsing the atom. Since atoms are stable, Rutherford's model is not completely correct.
Notes
A revolving electron should lose energy and fall into the nucleus. Atoms are stable, so Rutherford's model is not completely correct.
Check yourself
Why is a circling electron accelerating?
What does Rutherford's model predict for an accelerating electron?
Atoms are in fact stable. What does this tell us?
- Its speed keeps doubling. A particle in a circular path accelerates because its direction keeps changing.
- It is pushed by the voltage of a battery. The acceleration comes from the changing direction of motion along the circle.
- Its direction keeps changing — correct. Yes!
- It should lose energy and fall into the nucleus — correct. Yes!
- It should gain energy and leave the atom. The model predicts the electron loses energy and spirals inward.
- It should stay on the same circle with no change. An accelerating electron should lose energy, so it could not stay on the same circle.
- Atoms have no electrons. Electrons were discovered by Thomson and are part of every atom.
- Rutherford's model is not completely correct — correct. Yes!
- Matter around us is slowly collapsing. In reality atoms are stable, which is why matter around us stays intact.