Question

An element can have atoms with different mass number but same chemical properties and some are also used in the field of medicine medicines in the treatment of diseases

Answer 1

They are ISOTOPES with same atomic number but differ in mass number due to difference in number of neutrons.they show same chemical properties bcz chemical properties depend on atomic number.
e.g C has 3 isotopes
C_12
C_13
C_14
Similarly Iodine 131 used for treatment of thyroid gland