Impact of Radioactive Decay on Matter

Instructor: Julie Zundel

Julie has taught high school Zoology, Biology, Physical Science and Chem Tech. She has a Bachelor of Science in Biology and a Master of Education.

While you've probably heard of radiation, how much do you know about the types of radiation? This lesson will focus on alpha, beta, and gamma radiation and their impact on living and non-living objects.

Types of Decay

You're at the dentist and she says, ''Timmy, your left molar is starting to decay.'' You have lots of questions. First off, what does she mean by decay? The term decay can be applied to lots of things: teeth, fruit, relationships and even atoms…. the list is long.

Decay means to disintegrate or to break down. So, while you contemplate the solution for your left molar, let's focus on the decay of atoms. Remember, atoms are made of a nucleus, which contains protons and neutrons, and surrounding this nucleus are tiny electrons. Radioactive decay is the breakdown of an atom's nucleus and results in the release of radiation. Radiation is energy that is released in the form of particles or waves. Atoms undergo decay to become more stable.

Artistic representation of an atom

Uh oh, she's getting a drill. Well, before she starts drilling on that molar, let's go over each type of radiation in more detail, including the effects of radiation on living and non-living objects.


The first type of radiation we'll focus on is alpha radiation where a nucleus breaks apart (or decays), resulting in two new atoms (one of which is an alpha particle). Okay, that all sounds confusing. Don't worry. Let's break down that definition.

Imagine a big atom and then picture it breaking apart into two new atoms: one small and one large. The small one is made up of two neutrons and two protons and is called an alpha particle. This alpha particle is also called a helium nucleus (or He) because helium also has two protons.

In order to understand this concept, check out radium, or Ra, which is a radioactive element (meaning it will probably undergo radioactive decay). When radium decays, it breaks up into a smaller atom (the alpha particle) and a larger atom, in this case the element radon, or Rn.

Radium decaying into radon and an alpha particle
alpha decay

When alpha particles are emitted they cannot travel far and move only two or three inches in the air. They can be stopped by a piece of paper or skin, but issues arise when they are inhaled or ingested.

Do you remember radon from before? Like radium, radon decays releasing alpha particles. Radon is a naturally occurring gas that seeps up from the ground. In some parts of the country, radon levels are high and the gas can leak into houses through cracks. As people breathe in high levels of radon, they are exposed to alpha radiation and it can cause lung cancer. In fact, radon exposure is the number two cause of lung cancer in the United States.


Ouch! I can hear that drill starting up to get rid of the tooth decay. Meanwhile, the next type of radiation is called beta radiation where an atom releases an electron. This electron is referred to as a beta particle. There are different types of beta decay, but we are going to give a general overview so you don't get bogged down in details.

Beta decay causing beta radiation
beta minus

The image shows a nucleus made of protons (pink balls) and neutrons (blue balls). For the scope of this lesson, imagine that neutron is made up of protons and electrons and a particle called an antineutrino (it's a little more complex, but this works here). During beta decay, the neutron will spit out an electron and an antineutrino. Don't worry too much about the antineutrino; just picture it as another particle. When the neutron loses an electron, it changes into a proton. So, the entire process results in the loss of an electron and the gaining of a proton. This type of beta decay is called beta negative decay (and there is a beta positive decay, too, but don't worry about that here).

Beta negative decay, notice the new atom has an extra proton

These beta particles are not as heavy as alpha particles and can move further through the air. They can travel through paper and into the skin but can be stopped by a chunk of plastic, wood, or metal. The beta particle is 8,000 times smaller than an alpha particle so it can get into places alpha particles cannot. In living organisms, they can cause burns and skin damage. Ingesting or inhaling a beta particle can cause damage that results in cancer.


The last radiation we will discuss is gamma radiation, which occurs when the nucleus reshuffles itself and release a gamma ray. Unlike the other two types of radiation we discussed, a gamma ray has no charge and is a wave, not a particle. Sometimes the nucleus does not need to release particles in order to become stable and can rearrange its protons and neutrons. The result is the release of a gamma ray.

Gamma decay results in a gamma ray

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