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Radioactivity is often associated with disasters like the nuclear fallout at Chernobyl. But did you know that radioactivity is used in medicine, academics, industry, and even in generating electricity? So, what is radioactivity? It happens when an unstable atom emits radiation to become stable.

Why does radioactivity even occur?

Everything around us is made up of stable atoms. If they weren't stable, your table would turn into something else! Inside the atom's nucleus, some particles called protons are positively charged, while others called neutrons are neutrally charged. Normally, protons and neutrons repel each other, but a special force called the strong nuclear force keeps them together. This force only works over a short distance and depends on the ratio of protons to neutrons in the nucleus. Carbon 12 is an example of a stable element with six protons and six neutrons. However, carbon 14 has eight neutrons and six protons, making it an unstable isotope. Isotopes are formed when the proton count is the same as the stable atom, but the neutron count is different.

Unstable isotopes emit particles with energy as a way of restoring balance. During this process, the isotope forms a new nucleus. This property of turning from one thing into something else to attain stability is called radioactivity. Radioactive decay is the process in which an unstable atomic nucleus releases energy to become stable. Materials that have unstable nuclei are, therefore, radioactive.

Radioactivity: Radioactive decay

Unstable isotopes with three kinds of energy particles, which means that there are three types of radiation that are released by an unstable nucleus.

Radioactivity: Alpha (α)

An alpha particle has a helium nucleus that consists of two protons and two neutrons.

Alpha particles are somewhat heavy and only travel a few centimeters. Alphas are not that harmful either, as they can be easily halted by a sheet of paper or plastic.

Radioactivity: Beta (β)

When a nucleus of a heavy element undergoes a conversion, it can emit either an electron or a positron. This happens when neutrons inside the nucleus are converted into pro are called particles more energy than alpha radiation. Unlike alpha particles, beta particles can travel longer distances. However, they can be stopped by a thin sheet of metal or by protective clothing.

 The emission of an electron or a positron constitutes a beta-minus or a beta-plus decay.
The emission of an electron or a positron constitutes a beta-minus or a beta-plus decay.

Radioactivity: Gamma (γ)

Gamma radiation is by far the most dangerous form of radiation, as it has the smallest wavelength and the highest energy amongst all waves in the electromagnetic spectrum (Figure 3).

The rate of decay of a radioactive substance is determined by its half-life, which is the average time it takes for unstable nuclei to halve. This can vary for different elements, as it may take seconds, weeks, months, years, or even centuries. For example, the half-life of tritium (3H) is 12.3 years, while the half-life of uranium-238 is 4.5 billion years.

A long half-life can be dangerous because of the danger caused by radioactive elements. We need to be careful when it comes to storing or disposing of nuclear waste products because they can have a very long half-life and can damage the environment if radiation is released into the air, land, or water.

Do all radioactive isotopes decay at the same rate?

Isotopes do not all decay at the same rate. Most isotopes are stable. Hydrogen, for instance, has three isotopes, only one of which is radioactive while the other two are stable. For elements that do decay, radioactive decay is a very random process. To predict which nuclei will decay and when is, therefore, difficult. However, if you take a very large number of nuclei, their behavior can reveal a certain pattern because the rate of decay for a given isotope over a specific period is constant. This means that during that period, a predictable number of nuclei will decay. The rate of decay is measured by the decay constant (λ), which estimates how much a nucleus will decay per second. A larger value of λ indicates a faster rate of decay. For instance, when λ is twice as large, the decay rate per second is twice as high. See the formula below:

Activity = decay constant ⋅ number of nuclei

Radioactivity: Is radiation harmful?

Ionizing and nuclear radiation have been categorized as harmful for all biological beings. Some radiation can even be deadly.

However, low levels of radiation are not dangerous. Examples of this include the radiation emitted by your phone when you receive a call, the light bouncing off of your skin, and the food being heated in a microwave.

Even radioactive material can be put to good use. While exposure to limitless amounts of radioactive material can cause lethal amounts of genetic mutation and cancer, controlled amounts of the same material can be used to cure cancer. Radioactive iodine, for instance, is used in radiation therapy to treat cancer and for imaging in the thyroid gland.

Great summary! Here are a few minor edits:

  • An atom becomes unstable when the number of neutrons either exceeds or falls short of the number of protons.
  • Gamma rays have the shortest wavelength but the highest energy among all waves in the electromagnetic spectrum.
  • The decay constant (λ) estimates how much a nucleus will decay per second, and the larger the value of λ, the faster the rate of decay.
  • Ionizing or nuclear radiation can be harmful to biological organisms.
  • Radioactive iodine is sometimes used to treat cancer.


What is radioactivity? 

Radioactivity is the state in which an unstable atom emits radiation to achieve stability. 

What is radioactive decay? 

 Radioactive decay is the process by which an unstable atomic nucleus loses energy. 

Are all isotopes radioactive? 

No, not all isotopes are radioactive. 

Is Chernobyl still radioactive? 

Although the radioactivity has decreased with time, Chernobyl is still a radioactive area. 

Is Hiroshima still radioactive? 

No, it is safe to live in Hiroshima.

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