What is an isotope?
A clear starting point for anyone who wants to understand isotopes and why they matter.
Every element is defined by the number of protons in its atoms. Carbon always has 6 protons. Uranium always has 92. That number is fixed for each element.
The number of neutrons, however, can vary. Atoms of the same element that have different numbers of neutrons are called isotopes.
For example, most carbon atoms have 6 neutrons (carbon-12). Some have 7 (carbon-13). A very small number have 8 (carbon-14). These are all carbon, but they are different isotopes of carbon.
Stable and unstable isotopes
Some isotopes are stable. They remain as they are indefinitely.
Others are unstable. Over time they transform into different isotopes or elements and release energy in the process. These are radioactive isotopes, also called radioisotopes.
The energy and particles released by radioisotopes are what make them useful in medicine, industry, energy systems, and research.
Why isotopes matter
Isotopes are embedded in critical systems:
- Medical imaging and cancer therapy
- Nuclear energy and advanced reactor systems
- Quantum computing and precision materials
- Industrial measurement, tracing, and sterilization
- Space power systems and strategic applications
In many of these areas, specific isotopes are irreplaceable. Their availability depends on specialized production facilities and supply chains.
How isotopes are made
Most of the isotopes used in technology do not occur in useful quantities in nature. They have to be produced.
The two primary methods are:
- Nuclear reactors — materials are placed in a high neutron environment and transformed into the desired isotopes.
- Particle accelerators — beams of particles are used to create specific isotopes through nuclear reactions.
A smaller number of isotopes are obtained through other specialized processes, including enrichment of stable isotopes.
Where to go next
Once the basics are clear, move into the resource hub: