Pb has an atomic mass of 82. if an atom of that element has an atomic mass of 80, that atom is known as a. magnetic. b. an isotope. c. radioactive. d. a stereoisomer.

B. And isotope

Isotopes are atoms that have the same number of protons but different numbers of neutrons in the nucleus.

For a given element, its isotopes have

By changing the number of neutrons in the atom of Pb, the Atomic mass will decrease. In this case, the atom of Pb has 2 neutrons less than than Pb itself

the answer is definitely a