Proton Vs Nuetron
The atoms have a nucleus with protons and neutrons in it and then electrons that orbit around the nucleus all atoms are identical with 29 protons and 29 electrons. Since the atomic mass of copper is 63.55, there must also be 34.55 neutrons in all copper atoms. Only one isotope of copper is possible since all of the atoms will have the same nubmer of nutrons. Protons and nuetrons have a lot larger mass than electrons so they occupy the most volume in the atom. Since copper is in the third period in the periodic table the 29 electrons are distributed as evenly as possible between these three shells that means roughly 10 electrons per shell. Since there are only 29 electrons and the first shell is smaller, it will have 9 electrons in it with 10