Which of the following best explains why the mass number of a neutral atom is usually…
CHEMISTRY · Single correct · AP · Chemistry · Atomic Structure and Properties · Atomic Structure and Properties
Problem
Which of the following best explains why the mass number of a neutral atom is usually very close to an integer value?
(a) Because the atomic mass unit is defined as the mass of a single proton, each proton added contributes exactly 1 u, so the total mass is an integer multiple.
(b) Electronic binding energies are integral multiples of 1 u, so they adjust the total atomic mass to an integer.
(c) Because the nucleus contains nearly all of the mass and each nucleon’s mass is close to 1 u, the total mass of the atom is nearly an integer multiple of this unit.
(d) Isotopes whose masses are not close to integers rapidly undergo beta decay until the atomic mass reaches an integer value.