MediumChemistryHigh School (9–10)GeneralStructure of the Atom › Subatomic Particles and Atomic ModelsConceptualBoard Exam
Match each observation of the gold foil experiment with what it tells us…
Contributed by StemPy LabTry it on paper first. A hint, the key idea and the worked solution are here when you need them.
Match each observation of the gold foil experiment with what it tells us.
Observations:
(1) Most alpha particles passed straight through the foil.
(2) A few were turned through small angles.
(3) A very few bounced straight back.
Conclusions:
- The positive charge and almost all the mass are packed into a very small nucleus.
- The atom is mostly empty space.
- The nucleus is positive, because it pushes away the positive alpha particles that pass near it.
Need a reminder? The key ideaShow
In the gold foil experiment, most alpha particles passed straight through, a few were turned, and a very few bounced back. So an atom is mostly empty space, with a tiny, heavy, positive nucleus at its centre. The atom is about times wider than its nucleus.
The worked solution
Have you tried it?
Work it out on paper first. It is fine to get stuck or make a mistake: that is how we learn. When you are ready, go through the solution one step at a time, and check each step against your own.
Step 1. (1) with (b). Nothing stopped most particles, so most of the atom is empty space.
Step 2. (2) with (c). Particles passing near the nucleus were pushed aside, so the nucleus repels them: it is positive.
Step 3. (3) with (a). Only something tiny and very heavy could turn a fast alpha particle right round.
Answer: 1b, 2c, 3a.
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