Radioactive decay

Some tiny things are not still.

They let out energy. This energy moves away. This can change the tiny thing. It can even change what it is.

Scientists found this long ago. They used things that glow in the dark. These things let out rays. These rays can change one thing into another.

Some things stay this way for a long time. Other things change very fast. We cannot know when one tiny thing will change. But we can guess for a large group.

There are many kinds of these rays. Some are called alpha, beta, or gamma. These rays come from the center of the tiny thing.

Some of these things are found on Earth. They have been here for a very long time. They are part of our world.

Some tiny things are not still. They are called unstable nuclei. This means the center of the atom is not steady.

To become steady, these centers let out energy. This is called radioactive decay.

There are three main ways this happens. These ways are alpha, beta, and gamma decay. When an atom decays, it can change into a new element. This happens because the number of protons or neutrons changes. The starting atom is called the parent. The new atom is called the daughter.

We cannot predict when one single atom will decay. It is a random event. However, we can study a large group of atoms. We use a term called half-life to describe this. A half-life is the time it takes for half of the atoms to decay. Some half-lives are very short. Others last longer than the age of the universe.

Scientists like Marie and Pierre Curie studied this. They found new elements like polonium and radium. They also learned that these rays can be dangerous. Today, we use this science for medicine to treat cancer.

Everything in our world is made of tiny atoms. Most atoms are steady, but some have centers that are not stable. This unstable center is called a nucleus.

When a nucleus is unstable, it tries to become steady by letting out energy. This way it works is called radioactive decay. This process is also known as nuclear decay or radioactivity. It is a very important part of how the physical world works.

There are three common ways that an atom can decay. These are called alpha, beta, and gamma decay.

In alpha and beta decay, the atom actually changes into a different element. This happens because the number of protons or neutrons in the nucleus changes. The starting atom is called the parent radionuclide. The new atom created by the change is called the daughter nuclide.

This change of one element into another is called transmutation.

Scientists discovered these strange rays in the late 1800s. In 1896, Henri Becquerel found that uranium salts could make photographic plates turn black. Marie Curie later showed that these rays were a property of the atoms themselves. She and her husband, Pierre Curie, worked in a laboratory in Paris. They used their research to find two new elements named polonium and radium.

Other scientists like Ernest Rutherford helped explain how these elements decay using math. Rutherford and Frederick Soddy were the first to realize that decay changes one element into another.

Nature provides many examples of this science. There are 28 naturally occurring elements on Earth that are radioactive. These include well-known elements like uranium and thorium. There are also 35 primordial radionuclides that have existed since before our Solar System formed. One example is potassium-40, which is a long-lived radioisotope. We measure how much radiation is happening using a unit called the becquerel. One becquerel means one decay happens every single second.

We can see the effects of this science in our daily lives. For example, doctors use radiation to treat cancer in patients. This was one of the first peaceful uses of nuclear energy.

However, scientists also learned that these rays can be harmful to living things. Early researchers saw that X-rays could cause skin burns or hair loss. Because of this, groups like the International Commission on Radiological Protection were formed. They help create safety rules to keep people safe from radiation.

Radioactive decay is a fundamental process in physics. It occurs when an unstable atomic nucleus loses energy by emitting radiation.

A material containing these unstable nuclei is described as radioactive. This process is also called nuclear decay or radioactive disintegration. It is a vital concept for understanding how matter changes over time.

The mechanism of decay depends on different fundamental forces. Three common types of decay are alpha, beta, and gamma decay. Alpha and gamma decay are governed by electromagnetic and nuclear forces. Beta decay is driven by the weak force. In most cases, the process results in nuclear transmutation. This means the decaying nucleus, called the parent radionuclide, changes into a daughter nuclide.

If the number of protons changes, the atom becomes a different chemical element.

Radioactive decay is a random process at the level of single atoms. Quantum theory states it is impossible to predict exactly when one specific atom will decay. However, scientists can predict the behavior of large groups of identical atoms. This overall decay rate is expressed as a decay constant or a half-life. The half-life is the time it takes for half of the atoms to decay. These durations vary immensely. They can range from nearly instantaneous to much longer than the age of the universe.

The history of this discovery began in the late 19th century. In 1896, Henri Becquerel discovered radioactivity using uranium salts. He noticed they could blacken photographic plates even when wrapped in black paper. Marie Curie later proved these rays were a property of the atoms themselves. She and her husband, Pierre Curie, worked in a Paris laboratory. They isolated two new elements, polonium and radium, through their research.

Later, Ernest Rutherford and Frederick Soddy realized that decay leads to transmutation. Rutherford also showed that decay follows a specific mathematical exponential formula.

Nature contains many radioactive substances. There are 28 naturally occurring radioactive elements on Earth. These include 35 primordial radionuclides that existed before the Solar System formed. Examples include uranium, thorium, and the long-lived potassium-40. Scientists measure radioactive activity using the becquerel (Bq). One becquerel represents one decay per second. An older unit is the curie (Ci). Today, one curie is defined as 37 billion disintegrations per second.

Early use of radiation led to surprising and dangerous discoveries. The discovery of X-rays by Wilhelm Röntgen led to many experiments.

Some early experimenters suffered burns, hair loss, or swelling. Because the biological dangers were not immediately understood, some companies sold radioactive "medicines." These included radium-containing waters and enemas. Marie Curie warned that radium was dangerous in untrained hands. By the 1930s, many of these products were removed from the market after people suffered bone necrosis.

Today, the study of radiation is connected to medicine and safety. The discovery of radium helped launch modern nuclear medicine, such as cancer treatments. To manage risks, organizations like the International Commission on Radiological Protection (ICRP) were formed. They develop systems to protect the public and workers. Researchers continue to study the effects of low-dose radiation. For example, studies have looked at the risks for survivors of atomic bombings. This science helps us use nuclear energy safely in our modern world.