What is Radiation? - Lesson for Kids: Definition & Examples

Instructor: Kaarin Goncz

Kaarin has taught science from K-12 to seniors and has a doctorate in Biophysics

While atoms are the basic building blocks of our universe, some atoms are unstable and will lose particles through the process of radiation. But don't worry, this process is perfectly natural! Radiation can be very helpful to humans -- but it can also be harmful. Let's go over why.

Atoms and Isotopes

Did you know that scientists have discovered 118 different types of atoms? Each atom has its own atomic number based on the number of protons it contains in the nucleus. For example, an atom of carbon has atomic number 6 because it has 6 protons, while the atomic number of gold is 79 because it has 79 protons.

Atoms contain two other types of particles called electrons and neutrons. Each atom has the same number of electrons as protons, but the number of neutrons in an atom can vary a lot. For example, some carbon atoms have 6 neutrons, some have 7, and some have 8 neutrons! Atoms that have the same number of protons but different numbers of neutrons are called isotopes.

Hydrogen has 3 isotopes that have the same number of protons (p) and different numbers of neutrons (n)
Hydrogen has 3 isotopes

Radiation and the Three Rays

Isotopes that have a stable combination of protons and neutrons in their nucleus are called stable, but some isotopes are unstable. The only way for an unstable atom to become stable is to lose particles! This process is called radiation, and an atom that loses particles is called radioactive.

There are three types of particles that an atom can lose through the process of radiation, or radioactive decay. The atom can lose two neutrons and two protons bound together, which is called an alpha particle, or it can lose a beta particle, or a gamma particle, which is a type of energy called electromagnetic radiation.

An unstable isotope loses an alpha particle through radioactive decay
Unstable isotopes go through radioactive decay to become stable

The Life of a Radioactive Particle

The strange thing about radiation is that scientists don't know when an unstable isotope is going to lose an atom. It could happen any time! But scientists do know how long it will take for half the atoms of an isotope to decay. This amount of time is called the half-life.

Remember carbon? The isotope with 8 neutrons is unstable, and to become stable, the isotope will decay by losing a beta particle. When this happens, the neutron turns into a proton, leaving the carbon atom with 7 protons, which means the unstable carbon atom has turned into a stable nitrogen atom. The half-life of this radioactive isotope of carbon is 5,730 years! Just for comparison, the half-life for a radioactive isotope of oxygen is really short and is only 2 minutes!

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