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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If you look out of the 2nd floor window at a lawn, chances are you can’t make out individual blades of grass. But you can still see the lawn. The same way we see things made of atoms even though we can’t see the atoms.
Some microscopes can actually make out atoms. I think nuclei, much less protons and neutrons, are still out of reach, but in any case we knew about them way before microscopes got even close to being able to see them.
> how did we know it is that element/compound that results in the test turning out a certain way
You got it the wrong way. First we observed that certain materials behave in a certain way. There’s a reddish metal that gets a green coating if left out in the air, and we decided to call it “copper” way before we knew about copper atoms. Only in the 18th and 19th century did scientists come to the conclusion that all matter is made up of atoms, and copper metal is made of copper atoms.
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