In a sample of pure copper all atoms have atomic numbers which are

Atomic number is one of the identity of a certain element. This entails how many proton are present inside the nucleus of the atom. The atom has three most well-known subatomic particles: (1) proton, (2) electron and (3) neutron. 

Both proton and neutron are found inside the nucleus while the electrons are in the energy level clouding outside the nucleus. 

The answer to this item therefore is that the atomic number of all the neutral atoms of copper is 29.