how are moles solely related to atoms, molecules and particles of elements and compounds?

Answer 1

A mole is actually just a number, so it can be used for anything (a mole of people is Avogadro's number of people). What is special about it, is that it is defined so that any particle with a mass in atomic mass units will have the same value in grams if you take the mass of one mole of that material (atom for element, molecule for compound). It allows chemists to connect measurements of mass in the lab to a count of the particles that are the smallest piece of that material. Anything that relates to number of particles must be true about moles - formula relations and reaction relations)