Types of Radioactive Decay and Their Effect on the Nucleus

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  • 0:06 Nuclear Radiation
  • 1:26 Nuclear Notation
  • 3:10 Alpha Decay
  • 4:28 Beta Decay
  • 5:48 Gamma Decay
  • 7:16 Lesson Summary
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Lesson Transcript
Instructor: Kristin Born

Kristin has an M.S. in Chemistry and has taught many at many levels, including introductory and AP Chemistry.

What is meant by the term 'radioactive'? In this lesson we will break down the three main types of nuclear decay particles and discuss their composition, their effect on the nucleus, and their applications.


What images come to mind when you hear the words 'nuclear radiation'? Most likely these words conjure up a graphic scene of three-eyed fish and glowing green ooze. There are many misconceptions flying around out there when it comes to nuclear radiation, and the best thing you can do is educate yourself on the subject. Who knows; someday you may be voting on whether a nuclear facility is built near you.

Nuclear Radiation

Did you know that less than 1% of all the radiation you are exposed to comes from the nuclear industry? Most of it comes from natural sources like rocks. You are even a little radioactive! Nuclear radiation comes from all kinds of different places. There is natural radiation from the sun, water, and even bananas. There are also man-made sources of radiation, like nuclear reactors, certain types of medicine, and the smoke detectors in your home.

What exactly is radiation, and how damaging is it? The amount of danger nuclear radiation presents depends on which type of radiation it is. Today we will be discussing the three most common types of radioactive decay: alpha, beta, and gamma. Before we do that, we'll first do a quick review of the nuclear particles you should be familiar with along with their nuclear notation.

With these carbon isotopes, the 6s represent the atomic number and the top number is the mass number
Atomic Number Description

Nuclear Notation

As you may recall, the two particles that are found in the nucleus are the protons and neutrons. Because the atomic number of an element is the number of protons its atom has, a proton essentially has an atomic number of 1. It also has a mass number of 1 because its mass is almost exactly 1 amu. These two numbers are so important that sometimes they are included in certain notation. For example, when we are distinguishing the difference between three carbon isotopes, notice they all the sixes on the lower left of the symbol. Those sixes represent the number of protons (or the atomic number). They all have the same atomic number because they're all carbon. The top number is the mass number, which is the number of protons and neutrons, because both protons and neutrons have a mass of 1. Each of these three isotopes has the same number of protons but different numbers of neutrons.

Particles in the nucleus can also be represented by this nuclear notation. Going back to the proton example, its atomic number of 1 and mass number of 1 can be represented a couple of different ways - sometimes as a p with the atomic number on the bottom and the mass number on the top. Sometimes a little + is put as a superscript to the p, indicating its charge. And sometimes it's even represented as a hydrogen nucleus with an H instead of a p, because most hydrogen atoms have an atomic number of 1 and a mass number of 1. When using nuclear notation, the neutron is almost always represented as a 1, 0, and n, the 1 indicating the mass number, the 0 showing the atomic number, and the n symbolizing that the particle is a neutron. Later on, you will see why representing particles like this helps us keep track of everything.

Alpha Decay

Alpa particles can be easily blocked by air, clothes and your skin
Alpha Particle Easily Blocked

Now let's move on to the most common types of nuclear decay. The first is alpha decay. In alpha decay, the nucleus emits an alpha particle, or a particle containing two protons and two neutrons. The nucleus is said to decay, or change into one that is a little lighter, one with four less particles. An alpha particle can be represented a couple different ways - first, with 4, 2, and alpha symbol, the 4 representing the mass number (the number of protons plus neutrons) and the 2 representing the atomic number (the number of protons). Instead of the alpha symbol, the symbol for helium (He) is sometimes used because it's really just a helium nucleus.

Alpha particles are relatively heavy and quite slow-moving. It is for this reason that they can be blocked very easily by air, paper, clothing, and even your skin. Ingesting an alpha-particle emitter would be dangerous because your inner tissues don't provide the protection that your skin does and the alpha particles could cause some tissue damage. One of the main sources of alpha particles is the element radon, which is a gas found in many rocks. If a lot of radon is inhaled, it can get in your lungs and damage lung tissue. Some homes are even equipped with radon detectors to warn you if the levels are getting too high.

Beta Decay

One way that beta decay is represented
Beta Decay Represented

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