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.

First, the atomic number is equal to the number of protons. Also, the mass number is protons plus neutrons, as electrons weigh so little that they are not included. So Atom A has 19 protrons and 21 neutrons, while Atom B has 20 protons and 20 neutrons. Answer A and B are not true because Atom A has 1 less proton than Atom B. Answer C is not correct because nucleons are either protons or neutrons, which both atoms have an equal number of, as they have a mass of 40. Therefore, the answer must be B.