For example, if you take a sample of human bone and put it under a microscope, how do you know if the atoms you’re seeing are calcium atoms? You can’t exactly count the protons on the inside, can you? Also, how do you distinguish between protons and neutrons? Do they reflect different wavelengths of light and so have different colours or something? I’ve also heard people saying that we can’t actually see atoms using microscopes, is that true? If so, how can we say something is made out, say, carbon, when we can’t see it? If the answer to that is that we have tests (flame tests for metals, precipitate tests, pH tests, etc…), then how did we know it is that element/compound that results in the test turning out a certain way? I have so many questions!
P.S. I know that nuclei aren’t really perfect spherical balls, but rather collections of protons and neutrons, which are spheres, in a classical, non-quantum-mechanical sense.
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>For example, if you take a sample of human bone and put it under a microscope, how do you know if the atoms you’re seeing are calcium atoms?
You isolate them and subject them to various tests and see that they react the way calcium atoms react.
>You can’t exactly count the protons on the inside, can you?
You can, actually. They have mass, and therefore weight. And the protons have electric charge, so can be deflected by an electric field. So we can determine how much of that mass is protons and (by extension) how much of that mass is neutrons.
>Also, how do you distinguish between protons and neutrons? Do they reflect different wavelengths of light and so have different colours or something?
Protons have a positive charge and neutrons have no charge.
>I’ve also heard people saying that we can’t actually see atoms using microscopes, is that true? If so, how can we say something is made out, say, carbon, when we can’t see it?
Well, you *can* see carbon. Look in the mirror, see yourself? You’re largely made of carbon. Go outside. Look at a tree. A lot of carbon there. Have a wife or morther? Check out the bling on her ring finger. Pure, concentrated carbon.
How do we know it’s carbon? Well, like calcium above, because it has all the properties we understand carbon to have.
> If the answer to that is that we have tests (flame tests for metals, precipitate tests, pH tests, etc…), then how did we know it is that element/compound that results in the test turning out a certain way? I have so many questions!
Because that’s how we defined it. We take a substance that we don’t know what it is. See how it reacts, slap a label on it, then anything else that tests in the same way we deduce is the same substance with the same label.
So if something has the same weight as carbon, same number of protons and neutrons, reacts with the same way with the same kinds of substances and, basically, is the same in all distinguishable ways, then it’s the same substance.
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