Copper has an atomic number of 29. How many protons and electrons does a copper ion with a charge of +2 have?

A copper ion with a charge of +2 has 29 protons and 27 electrons. 

The atomic number of an element is equal to the number of protons in the nucleus of each atom of that element. Since copper has an atomic number of 29, all atoms of copper will have 29 protons. This is what identifies an atom as copper. 

Electrons are found outside the nucleus of an atom. An atom can gain or lose electrons during chemical reactions to form ions, which are charged particles. A neutral atom has an equal number of protons, which are postiviely charged, and electrons which are negative. If an atom loses electrons it forms a positive ion and if it gains electrons it forms a negative ion.

If a copper ion has a charge of +2 it means that it lost two electrons and now has two more protons than electrons.