The atomic weight of copper, Cu, is listed as 63.546. Which of the following statements are untrue: Check all that apply. The dominant isotopes of Cu must be 63 Cu and 64 Cu. Copper is a mixture of at least two isotopes. The number of electrons in the copper atoms is independent of atomic mass. All the copper atoms have 29 protons in the nucleus. Not all neutral atoms of copper have the same number of electrons.