Answer
B. And isotope
Explanation
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
the same number of protons
different numbers of neutrons
the same number of electrons
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 Pb itself
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