When a proton is added to the nucleus of germanium (Ge), which has an atomic number of 32, the atomic number increases to 33. This means that the element changes to arsenic (As), which has an atomic number of 33.
Based on this information, the correct outcomes from the given options are:
A The atom would increase in mass but would remain germanium. - Incorrect (the element changes)
B The atom would become arsenic and have different properties. - Correct (the element changes to arsenic and will have different properties)
C The atom would remain germanium, but it would have a positive charge. - Incorrect (the element changes)
D The atom would increase in mass and have different elemental properties. - Correct (mass increases and the element changes)
E The atom would expel a neutron to maintain a constant mass and chemical properties. - Incorrect (it does not maintain constant mass or properties with the addition of a proton)
Therefore, the correct selections are B and D.