Why does increasing or decreasing the number of protons (as you move about the periodic table) drastically change how elements look and behave. How is it with slightly different quantities of the same thing get you from gold to salt to helium? Are those atomic particles really are there is to matter?
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There are many ways you can measure physical properties, and the periodic table of elements helps us organize our thinking about them.
There is a [good higher level FAQ here – The periodic table and the physics that drives it](https://www.nature.com/articles/s41570-020-0195-y) (or get the PDF [here](https://annas-archive.org/search?index=&q=The+periodic+table+and+the+physics+that+drives+it&content=journal_article&sort=)
Basically we can break it down into physical properties (solid, liquid, gas, melting point etc) and chemical properties (what does it react with, and how).
On the far right of the table are a group called the noble (non reactive) gasses.
They have similar non reactive chemistry because all their electrons are in a stable state without either “extra electrons” looking to react with something else, or an “electron deficiency” looking for extra electrons to react with it.
They have similarities in physical state (gas at room temp and 1 ATM pressure)
They get heavier as you go from He to Rn.
If you look at the first column (aka Group 1) you get things that are highly reactive. Except for H, they are all solids.
The atomic and subatomic physics that leads to this regular patter was unknown in the 1800s when Dmitri Ivanovich Mendeleev put a small periodic table together.
in 1911 Ernest Rutherford’s discovery of the atomic nucleus gave us a theoretical reason for why this happens.
The old explanations mostly used concepts like orbitals, but modern physics makes it more complex.
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