How do isotopes of an element differ?

Isotopes of an element differ in the number of neutrons they have in their nucleus.

Isotopes are variants of a particular chemical element, which means they belong to the same element and have the same number of protons in their atomic nucleus. However, they differ in the number of neutrons. This difference in neutron number results in different atomic masses for the isotopes of the same element. For example, hydrogen has three isotopes: protium (no neutron), deuterium (one neutron), and tritium (two neutrons).

The term 'isotope' comes from the Greek words 'isos' meaning 'same' and 'topos' meaning 'place', referring to the fact that different isotopes of an element occupy the same position on the periodic table. Despite their differences in atomic mass, isotopes of the same element exhibit nearly identical chemical behaviour. This is because the chemical properties of an element are determined by the number of protons and electrons, which is the same for all isotopes of a given element.

However, isotopes can have different physical properties. For instance, they can differ in their stability. Some isotopes are stable and do not change over time, while others are unstable or radioactive, meaning they decay over time and emit radiation. This radioactive decay can be used in various applications, such as medical imaging and treatment, archaeological dating, and nuclear power.

In summary, isotopes of an element have the same number of protons but differ in the number of neutrons, leading to differences in atomic mass and physical properties, particularly stability.