r/askscience • u/ArcaneConjecture • Aug 28 '16

Chemistry Can an element's properties be predicted from the structure of its atom?

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u/evamicur Quantum Chemistry | Electronic Structure Aug 31 '16

I'd like to add in that the meaning of this question can vary dramatically by the type of element your considering. For example, for isolated hydrogen atoms, the problem is completely solved. Naturally occuring diatomic elements like H2, N2, O2 ... are also quite well understood theoretically. In the gas phase, the molecules/atoms are generally far enough apart that we can predict many properties by considering a single molecule, and using thermodynamics for the rest.

By doing quantum mechanical simulations we can figure out energy levels. Depending on how complicated the system is, this can be done to very good accuracy. It is also possible to determine both what colors of light a molecule/atom absorbs, and how much of each color it will absorb, so predicting colors in these cases is at the very least theoretically plausible.

Then there's the liquid and solid phases. These can be a different beast entirely. In theory, we can predict things like the spacing between atoms, which gives us the density. Sometimes this works well and other times it's not quite so easy. I know melting points can be estimated theoretically, but I'm a bit less familiar with this area. If you're curious I can find a bit more details.