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Post by NS_Tutor_Thomas » Sun Dec 23, 2018 9:14 am

A student recently wrote us: "Third roman numeral should be worded better. I thought it was saying the overall charge of the alpha particle is +. I didn't understand it was referring to the nucleus at all."

The overall charge of an alpha particle is positive. They are the nuclei of He atoms. The reason why it has an overall positive charge is that it has 2 protons (positively charged) and two neutrons (neutrally charged).

I hope this helps. Thanks for your question!
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Re: NS FL3 C/P Q8

Post by samanthasheffels » Thu Aug 08, 2019 7:40 pm

So aside from knowing that there is some electrostatic repulsion and the + charge of an alpha particle, what from the passage tells us that Rutherford's observations were consistent with them both being +?

Because from the passage they only said some electrostatic repulsion, so even though it would make sense that they both would be + from what we know now, it didn't mention that he knew an alpha particle was + or that the gold would be +.
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Re: NS FL3 C/P Q8

Post by NS_Tutor_Mathias » Thu Aug 22, 2019 2:08 pm

This question is a bit backwards from what usually happens. Rather than reasoning about experimental design, you are reasoning from what you know to be true to explain phenomena Rutherford observed.

We can take the passage's word about "rebounding due to repulsive forces", and/or we should be aware from that as a matter of background knowledge for C/P. The same goes for RN I, which is something we should definitely be aware of, but the passage provides it, just in case.

In the end, all we are saying by answering this question is that Rutherford's experiments on the structure of a atom turned out the way they did because of the way an atom is structured (unsurprising). And we are saying that making sense of it is much easier now that we have additional insight.

I see where you're coming from that trying to reason through this question may lead you to try to view this as an experimental design question, when you are simply asked for a list of things that are true about atomic structure.
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