Explain with examples: (i) Atomic number, (ii) Mass number, (iii) Isotopes and (iv) Isobars.

(i) Atomic Number:
– Definition: The atomic number (Z) uniquely identifies an element and represents the number of protons in the nucleus of an atom.
– Example: Take carbon (C) with an atomic number of 6. This means every carbon atom has 6 protons in its nucleus, distinguishing it from other elements.

(ii) Mass Number:
– Definition: The mass number (A) indicates the total number of protons and neutrons in an atom’s nucleus.
– Example: Consider carbon-12 (^12C). It contains 6 protons and 6 neutrons, resulting in a mass number of 12 (6 protons + 6 neutrons).

(iii) Isotopes:
– Definition: Isotopes are variants of an element with the same atomic number but different mass numbers due to varying numbers of neutrons.
– Example: Hydrogen has isotopes: protium (^1H) with only a proton, deuterium (^2H) with a proton and a neutron, and tritium (^3H) with a proton and two neutrons.

(iv) Isobars:
– Definition: Isobars are different elements sharing the same mass number but having different atomic numbers.
– Example: Carbon-14 (^14C) and Nitrogen-14 (^14N) are isobars. Despite different atomic numbers (6 and 7, respectively), they share a mass number of 14.

Uses of Isotopes:
1. Radiometric Dating: Isotopes like carbon-14 are employed in dating organic materials, helping archaeologists determine the age of ancient artifacts.
2. Medical Diagnosis and Treatment: Isotopes like technetium-99m are used in nuclear medicine for imaging techniques like PET scans and in radiation therapies for cancer treatment.

These concepts are fundamental in understanding atomic structure and behavior. Atomic number defines an element, the mass number signifies the total particles in the nucleus, isotopes vary in neutron count, and isobars are distinct elements sharing the same total atomic mass. Isotopes, due to their differing properties, find critical applications in diverse fields such as archaeology and healthcare.