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:

Isotopes are atoms of the same element that possess the same atomic number (number of protons) but different mass numbers due to a variation in the number of neutrons. This makes statement 1 correct. Isobars are defined as atoms of different elements that have the same mass number (total nucleons) but different atomic numbers. Statement 2 is incorrect because it describes isotones. Isotones are atoms of different elements that have the same number of neutrons but different atomic numbers. Statement 3 is incorrect because it provides the definition for isobars instead of isotones. Therefore, only the first pair is correctly matched. These concepts are fundamental to understanding atomic structure and nuclear stability, where the atomic number (Z) defines the element and the mass number (A) represents the sum of protons and neutrons.