Learn: Isotopes and Why They Exist

Welcome!Welcome back! You've already learned about protons, neutrons, and electrons, including their relative charges and masses. Today, we'll build on that by exploring isotopes—what they are, why they exist, and why they're important in chemistry.

What Are Isotopes?Isotopes are atoms of the same element with the same number of protons but different numbers of neutrons. This means they have the same atomic number but different mass numbers. Isotopes exist because the number of neutrons in an atom can vary while still keeping the atom stable.

Why Do Isotopes Exist?Isotopes exist because adding or removing neutrons does not change the chemical properties of the element—it still has the same number of protons. However, the number of neutrons affects the atom's mass and can influence its stability, leading to radioactive isotopes in some cases.

Mass Number and Atomic NumberThe atomic number represents the number of protons in the nucleus and defines the element. The mass number is the total of protons and neutrons in the nucleus. Isotopes have the same atomic number but different mass numbers.

Stable and Radioactive IsotopesSome isotopes are stable, meaning they do not decay over time, while others are radioactive, meaning they break down and emit radiation. For example, carbon-12 is stable, but carbon-14 is radioactive and used in carbon dating.

Examples of IsotopesConsider hydrogen: it has three isotopes—protium (1 proton, 0 neutrons), deuterium (1 proton, 1 neutron), and tritium (1 proton, 2 neutrons). All are hydrogen because they have one proton, but their mass numbers differ.

Review Time!Great work! So far, we've covered isotopes, their definition, and why they exist. Let's test your understanding of these concepts.

Well Done!You've successfully learned about isotopes and why they exist. Keep practising to deepen your understanding, and feel free to ask questions if anything is unclear!