When substances like uranium and carbon-14 break down over time, they emit radiation. This is a process called radioactive decay. This natural process happens when unstable atoms release energy to become more stable. We see it in the world around us: the earth beneath our feet, the air we breathe, even within our bodies.
This article explores what happens during radioactive decay and half-life, which is an important related topic. We'll discuss practical applications of this transformation, such as medical treatments, and safety precautions to follow when handling radioactive materials. This guide is suitable for GCSE students revising for their exams. It covers all exam boards, including AQA.
If you need more help understanding the science behind radiation, TeachTutti has vetted GCSE Science tutors who can support your learning, such as making revision notes.
What is radioactive decay?
Radioactive decay is a random process that begins in the nucleus of an atom. An atom is normally stable, with a balanced number of protons and neutrons in the nucleus. Atomic nuclei are unstable when this combination is unbalanced. These unstable atoms are called radioactive isotopes. They spontaneously release particles or energy to achieve stability, known as radioactive decay.
For example, picture a shaky stack of building blocks. It may seem stable, but pieces will eventually start falling off until the structure is more stable. This is what happens when radioactive nuclei "shed" energy to achieve stability. As mentioned, this decay happens naturally and at random. Scientists can't predict when an atom will decay. Instead, we use probabilities to determine how likely decay is over time.
This process isn't affected by external factors, e.g. temperature or chemical reactions. It is a nuclear process that is caused by changes inside the nucleus. It is unique and very different to other chemical reactions you are learning in the GCSE curriculum.
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What statement about radioactive decay is correct?
Types of nuclear radiation
There are three main types of radiation caused by radioactive decay: alpha particles, beta particles and gamma rays. Each type has unique properties, such as the ability to penetrate materials.
Alpha particles
There are two protons and two neutrons in alpha particles. This is the same as a helium nucleus. Alpha particles are positively charged and one of the heaviest forms of radiation. They are less able to penetrate materials, travelling a short distance in the air and being easily stopped by thin barriers, e.g. paper or human skin. This is due to their mass and size.
Alpha particles can be very dangerous if ingested or inhaled. They are capable of damaging cells from within.
Beta particles
Beta particles are high-energy, fast-moving electrons emitted by the nucleus of a radioactive atom. They have higher energy levels and move quickly, being able to penetrate through paper and even thin metal sheets like aluminium. This is because beta particles have a smaller mass and carry a negative charge. They can normally be stopped by thick barriers, like dense plastic.
They are less dangerous but can still cause significant damage, such as when exposure is prolonged or internal.
Gamma rays
Gamma rays are not even particles, which separates them from alpha and beta particles. Instead, they are high-energy electromagnetic waves. They carry no mass or electric charge, penetrating deeply through the human body, walls and even metal. They are potentially very dangerous. To shield effectively against gamma rays, scientists need to use dense materials, such as lead or thick concrete.
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What radiation can penetrate furthest through materials?
Half-life
The half-life is how long an unstable nucleus in a radioactive sample takes to decay. For example, let's say we have 100 atoms of a radioactive isotope. After the first half-life, there will only be 50 atoms remaining undecayed. The second half-life will leave 25 atoms. This process can be over in a fraction of a second or last for billions of years.
Carbon-14 is used in radiocarbon dating, which is a method to find the age of organic materials. It has a half-life of roughly 5,730 years. Scientists can work out how many half-lives have passed in an archaeological object by measuring the amount of Carbon-14. This can accurately explain the age of the object.
In contrast, the half-life of radioactive isotopes in medical treatments is much shorter. This ensures they don't remain in the patient's body for any longer than necessary.
Half-life is an effective method to predict radioactive decay. We can't say when an atom will decay, but knowing the half-life lets us predict how long an amount of radioactive material will take until it decays to a safer level.
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A radioactive sample has a half-life of 2 hours. How much of the sample will remain after 4 hours?
Uses of radiation
Radioactive isotopes have unique properties. Many practical applications have been developed by scientists and engineers that are embedded in our daily lives. These include medicine, archaeology and energy production.
Medicine
Gamma rays are used in radiotherapy to target and destroy cancer cells. Radiation is used in precise doses to target tumours directly and avoid damaging surrounding tissue.
Medical imaging also relies on radioactive isotopes. For example, Positron Emission Tomography (PET) is a scanning technique that uses short-lived radioactive isotopes. It creates detailed images of organs, helping doctors to diagnose diseases early and accurately.
Archaeological dating
Radiocarbon dating is used in archaeology. Every living organism regularly absorbs a small amount of radioactive carbon-14 from the atmosphere around it. When we die, the body stops absorbing carbon-14, and the existing carbon-14 begins to decay inside the body.
Scientists measure the remaining carbon-14 to calculate when the organism died. This is crucial for archaeologists to accurately date ancient artefacts, fossils, and historical sites.
Dinosaur bones are not an example of radiocarbon dating. The half-life of carbon-14 is too short to analyse fossils that are millions of years old.
Energy production
Nuclear energy relies on controlled radioactive decay.
A nuclear reactor uses uranium isotopes to undergo decay through a process called nuclear fission. This splits the nuclei of unstable uranium and releases a huge amount of energy in the form of heat. This energy is used to generate electricity. Nuclear power is increasingly used to provide electricity for countries and is an efficient, low-carbon energy source. As of 2025, the UK generates approximately 12% of its energy from nuclear power.
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What is commonly used in radiocarbon dating?
Safety and precautions
While radioactive decay has many benefits, there are also inherent dangers in radiation. Cells and tissue can be damaged by exposure to radiation, especially if this is prolonged or intense. This can cause burns and radiation sickness. It can also lead to an increased risk of cancer. Stringent safety measures need to be followed when working with radioactive materials.
Limiting exposure
Three factors help minimise radiation exposure:
Time - The longer you are exposed to radiation, the greater the dose you receive. Professionals working with radiation monitor their exposure closely and limit the time they spend near radioactive sources.
Distance - Keep enough distance from the radioactive source. The intensity of radiation decreases significantly with distance. Laboratories and hospitals follow this principle: radioactive materials are kept at a safe distance and remote tools are used where possible.
Shielding - The shielding depends on the radiation type. Alpha radiation can be blocked by paper, clothing, or skin. Beta radiation needs a thicker barrier, like aluminium. Gamma radiation is the most dangerous and needs thick shielding, such as lead.
Safe handling of radioactive materials
Protective clothing should always be used when working around radioactive substances. Professionals will always wear clothing that avoids contamination, such as gloves and lab coats. They can monitor the radiation levels using Geiger counters or radiation badges. The radioactive material itself should always be stored in a well-marked, shielded container. This will prevent accidental exposure.
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Which material should you use to shield against gamma rays?
Final thoughts - Nuclear radiation, GCSE Physics
Radioactive decay is a natural phenomenon found in the nucleus of an atom. It has wide-ranging applications, from medical treatments to historical research. It also creates clean energy, which is increasingly important in the face of climate change.
Keep in mind that radioactive decay happens spontaneously and at random. Each type of radiation released from this decay has unique characteristics and accompanying risks. Half-life helps scientists to predict how long a radioactive isotope will take to decay, and safety measures are crucial to minimise exposure when working with these materials.
For further reading, learn about nuclear fission and fusion with this guide by the International Atomic Energy Agency (IAEA). You can also read this detailed article on the uses of radiation by the United States Nuclear Regulatory Commission.
If you need additional support to revise nuclear radiation, TeachTutti have experienced GCSE Science tutors. Lessons can be in-person or online. Tutors will tailor lessons to your specific needs and every tutor has an enhanced DBS check.
This post was updated on 30 Nov, -0001.
