Which of the following pairs is/are correctly matched? 1. Isotopes : Atoms with same atomic number but different atomic mass 2. Isobars : Atoms with same number of neutrons but different atomic number 3. Isotones : Atoms with same mass number but different atomic number Select the correct answer using the code given below : Code:1, 2 and 3 1 only1 and 2 only2 only