67th B.P.S.C. (Pre) 2021
Isotopes of an element differ in -
aThe number of protons
bThe mass number✓ Correct
cThe number of electrons
dThe atomic number
eNone of the above / More than one of the above
Explanation
Elements having the same atomic number are called isotopes; that is, those whose atomic number (number of protons) is the same, but whose mass number or atomic weight is different, are called isotopes. Elements having the same atomic weight are called isobars. In isotopes, the number of protons is the same, but the number of neutrons is different.
general-science