The nucleus of an atom of the copper isotope 63Cu contains 29 protons and 34 neutrons. How many electrons must be removed from a neutral 63Cu atom to completely ionize it, leaving only a nucleus

27 electrrons

Explanation:

Number of protons = 29

Number of neutrons = 34

Recalling that the number of protons is equal to the number of electrons as in the definition of atomic number of an element.

Hence, for an ion or a cation such as copper with + 2 on it, it implies it has lost 2 electrons and as such the remaining number of electrons to completely ionize it will be 27 electrons.