Is it hard to push two protons tightly together? why? (think about charge)

In the 1800s, one of the statements in john dalton's atomic theory was that atoms are indivisible. later experimental evidence led to the discovery of subatomic particles such as neutrons, electrons, and protons. what happened to the indivisible atom part of dalton's atomic theory, and why?

What are the first three quantum numbers for the electrons located in subshell 2s?

Once similarity and one difference between a mixture of elements and a mixture of compounds