I've read this question What would the periodic table of a 4-Dimensional universe look like?, and I think it answers part of my question about how atomic physics would work, but I'm not sure. Would a 2-dimensional atom have any rotational axis? How would that affect the spin? How many orbitals would be in each energy level? I'm assuming that protons, neutrons, and electrons exist.
I moved this over to Physics. https://physics.stackexchange.com/questions/449678/what-would-the-periodic-table-look-like-in-2-dimensions
I'm assuming that protons, neutrons, and electrons exist
Not as we would know them. The atom in 2D would literally be the Neils Bohr model on paper, not anything like what we know of atomic structure $\endgroup$