Why is the ground state important to chemistry?
Thanks for your question about the atom.
The ground state refers to an unexcited atom where the electrons are in their lowest energy levels. Being able to determine where the electrons are in an unexcited atom allows us to tell where the excited electrons went to and returned from when they emit a photon.
Photons of electromagnetic radiation are emitted when an electron has absorbed energy, becomes excited, moved to a higher energy level, "spit" out its absorbed energy, and then returns to its original ground state.
The photon can tell us how many energy levels the excited level jumped.
Using the ground state of electrons can also tell us the fill order of electrons in an atom. According to the aufbau principle, electrons fill the lowest available energy level first. (they are lazy like me!!) When determining an electron configuration for an atom, we fill the lowest energy level first, then successively higher energy levels until we have the number of electrons that an ATOM of that particular element has.
I do hope this helps.