Atom a has an atomic number of 19 and mass number of 40. atom b has an atomic number of 20 and a mass number of 40. which of these is an accurate statement? a) atom a has more protons than atom b. b) atom a has one less proton and one more neutron than atom b. c) atom a has an extra nucleon compared to atom b. d) atom a has one more proton and one more electron than atom b.