Atomic number refers to the number of protons in an atom’s nucleus, defining the element. Mass number is the sum of protons and neutrons in the nucleus. Isotopes are atoms of the same element with the same atomic number but different mass numbers, meaning they have the same number of protons but a different number of neutrons. Isobars are atoms of different elements with the same mass number but different atomic numbers. Two uses of isotopes are as nuclear fuel (like uranium-235) and in medical treatments, such as treating cancer with cobalt-60.
Examples:
Atomic Number: Oxygen has 8 protons, so its atomic number is 8.
Mass Number: Oxygen-16 has 8 protons and 8 neutrons, so its mass number is 16.
Isotopes: Oxygen has several isotopes, including oxygen-16, oxygen-17, and oxygen-18, all with an atomic number of 8 but different mass numbers.
Isobars: Argon-40 (atomic number 18, mass number 40) and Potassium-40 (atomic number 19, mass number 40) are isobars. Isotopes have many applications, including medical imaging and cancer treatment. For example, radioactive isotopes like Iodine-131 are used in thyroid scans, and Cobalt-60 is used in radiation therapy for cancer.