The past Friday I attended a chemistry lecture at UCL university that was simply fascinating, the lecturer was talking about the atom and its history. This article will not be purely scientific, there will also be a philosophical aspect to it. Questions will be asked and you can comment whether or not you believe that these questions have actually been answered to a sufficient enough degree. Questions like; how do we know what we know? since we can’t see atoms how do we know anything about it really? Is it just made up?
This question goes back to Democritus who is from the ancient Greeks. The ancient Greeks were known for their philosophy, they came up with a number of mind blowing paradoxes. Are things infinitely divisible? Can we continuously cut gold in half forever? Would we reach a point where cutting it in half is no longer possible? Democritus believed in atoms, it had to exist and this was an idea that was denied because if they do exists, within something there had to be spaces of nothing and this was something that seemed to be impossible to them in their minds.
Fast forward in time we come to scientists. Joseph Priestley and Henry Cavendish. Priestly discovered the oxygen atom, laughing gas and invented carbonated drinks! He discovered the oxygen atom along with Cavendish. He discovered that when you burn hydrogen with oxygen you create water, this led to the discovery of molecules and compounds and how they are made up of different elements. At this point in time we still can’t see these atoms, microscopes can not be used to see atoms as the microscopes used visible light, and the wavelength of visible light is 500nm and you can look to about as low as 250nm which is still far too wide to see an atom.
The diffraction grating is a physics technique, which uses light diffraction and this equation, nλ=d sin(θ), which helps you to attempt to ‘see’ the atoms. After they discovered X-ray, they also discovered that x rays are a lot thinner and therefore the diffraction grating would help even more. They didn’t know the harmful effects and in fact to find where the x days were, they would wait till their eyes got warm and that is how they knew it was going right through them!
Crystals are a natural phenomenon and this could be used as a diffraction grating, this would be used to diffract the X-rays moving right through them, and an image would be formed and this would then would be calculated to find the space between atoms. But looking at these images is very strange, it is all a reciprocal space which is like mirror image but worse. Everything is inverse, large distances are short and vice versa. Diffraction images are really hard to interpret.
See the pattern below, this image shows a reciprocal image. Rosalind franklin used this and got famous because of this. A quick interpretation of this is that the dots that are far are short, so a concave shape would be the opposite. This cross shape shows the repeating unit and the appearing of the double helix. Watson and Crick guessed this and Franklin insisted for more evidence for DNA before making a jump.
Fourier transform is the process of using maths to transform reciprocal space to real space, and these new techniques could be used to help us. Real images show pictures like this- which is the electric density map of copper. Discovering that the atoms were really just spheres very similar to what the Greeks theorized.
Is this the end of the story? No.
Electrons are not particles, electrons are actually waves and they do not really orbit around the nucleus like the sun. n=1 oscillation, n=2 oscillation, n=3 oscillation are different types of oscillations, the more energy the electrons have the greater the oscillation. The electron waves are 3D. It is astonishing as our knowledge has been inversed really, we thought that light were waves but in reality, they are photons and we thought that electrons were particles when in reality they are waves.
In the photoelectron effect, if you shine a light in the right colour, electrons come out. If you shine blue lights which have photons with more energy electrons leave and we can record the energy of the electrons coming out. The red light would not cause it to come out. This does not sit with atoms being spheres since electrons are waves.
Finally ‘the truth’ and our knowledge of the ‘truth’. A scientific truth is really like a theory that is very good. Atoms are now studied more in quantum mechanics, but what truth do we really know and the truth is something that might not be anything similar to what we know, like atoms being spheres contrary to the very popular belief, a belief I once held before going to a chemistry lecture. Like to end this long article with a quote from Indiana Jones:
“Science is the search for fact, not truth. if it’s truth you’re interested in, there’s a philosophy class right down the hall”
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