Radioactive Elements

Contributor: Hannah Brooks. Lesson ID: 12499

You have no doubt heard about radiation fallout from bombs and nuclear power plant meltdowns. What causes radiation, and why is it so dangerous? What causes those microscopic atoms to become deadly?



learning style
personality style
Grade Level
High School (9-12)
Lesson Type
Dig Deeper

Lesson Plan - Get It!


Have you ever been x-rayed? Why does the radiologist wear or hide behind a lead shield? Why should you avoid going near or touching radioactive materials?

You might have heard that radioactivity can be dangerous to your health, but why is that?

Well, radioactivity can damage the cells in your body, causing issues from burns to cancer. Radioactivity comes from naturally-occurring elements in our environment.

Many of these elements have an atomic number greater than 83. That means that the atoms of these elements contain more than 83 protons.

Protons are held in the nucleus of the atom. Some elements are radioactive because of the number of neutrons they hold, even though they don't have 83 protons. Neutrons are also found in the nucleus. Atoms of an element with the same number of protons, but a different number of neutrons, are called isotopes. Carbon has three isotopes, as shown below:

The nucleus of a radioactive element can break apart at any time because it is too large and unstable. When the nucleus separates, energy is lost in the form of radiation. The process of nuclear breakdown is measured using half-life.

Half-life describes the amount of time it takes for half of a sample of a radioactive element to degrade, or break down. That means half of the atoms of the element have undergone nuclear decay. Different elements have different half-lives. Radium, an element used to make glow-in-the-dark watches before the 1970s, has a half-life of 1,600 years! The half-life of uranium, an element used in energy generation, is 4.5 billion years!

Radiation released from the nucleus of an atom can be measured by a Geiger counter. This tool reads the amount of radiation in an area by creating an electrical charge in the presence of radiation. Gieger counters can help keep scientists and individuals safe because they are aware of the amount of radiation exposure.

Summarize what you have learned in a three- to five-sentence paragraph that describes common characteristics of radioactive elements.

Radioactive elements release energy from the atomic nuclei as the nucleus breaks down. Elements with more than 83 protons are considered radioactive, and have many protons and neutrons held in the nucleus. Radioactivity can be detected by a Geiger counter, a tool that responds to radiation.

In the Got It? section, you will learn more about the three types of radioactive decay that radioactive elements experience.

Elephango's Philosophy

We help prepare learners for a future that cannot yet be defined. They must be ready for change, willing to learn and able to think critically. Elephango is designed to create lifelong learners who are ready for that rapidly changing future.