# Rutherford's gold foil experiment [duplicate]

Rutherford projected $\alpha$-rays onto the gold foil. $\alpha$-rays are the same as a $\ce{He^2+}$ nucleus and they can ionize atoms. Therefore, why are gold atoms not ionized when the $\alpha$-rays collide with them?

## marked as duplicate by Mithoron, Todd Minehardt, pentavalentcarbon, airhuff, Pritt BalagopalJun 26 '17 at 5:45

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• Since electronic stopping (interaction of ions with electrons) is well known, the answer is the alphas did lose energy to electrons in the film. These low momentum interactions spread the beam. The spread of the transmitted beam was measured by Geiger and Marsden. – Jon Custer Jun 25 '17 at 16:30

## 1 Answer

In Rutherford's experiment to show the existence of nucleus in an atom, the alpha-particles were exposed on the surface of certain metal i.e. gold. He observed that more than 99% of these particles were able to go straight and pass through the gold atoms. Thus he was able to conclude that atoms are mainly empty space. But why did these particles not collide with the electrons present in the gold atoms? I think that the reason behind it is that the speed of the electrons travelling in orbits did not cause any obstacle in the travelling path of the alpha particles.

• If you have a new question, please use the Ask Question button and link to this question if necessary. – Glorfindel Jun 25 '17 at 16:18