Scientists Say: Radioactive

This word describes elements that shed energy over time

These watch hands are glowing because they have been painted with radium. Radium is a radioactive element, which gives off energy that causes nearby zinc sulfide to glow green.

Mauswiesel/Wikimedia Commons/ (CC BY-SA 3.0)

Radioactive (adjective, “RAY-dee-oh-AK-tiv”)

This word describes unstable elements. Each atom — the basic unit of elements — has dense centers. This is its nucleus. Each nucleus is made of positively charged protons and neutrally charged neutrons. These particles are subatomic — meaning they are smaller than the atoms they are part of.  When an atom is radioactive, this nucleus sheds energetic protons and neutrons over time. Those particles deposit some of their energy along the path they travel. Because they can deliver so much energy onto a tiny area, these subatomic particles can pose a risk to cells.

In a sentence

Radioactive elements such as plutonium can be carcinogens — substances that cause cancer.

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Power Words

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atom   The basic unit of a chemical element. Atoms are made up of a dense nucleus that contains positively charged protons and neutrally charged neutrons. The nucleus is orbited by a cloud of negatively charged electrons.

cancer  Any of more than 100 different diseases, each characterized by the rapid, uncontrolled growth of abnormal cells. The development and growth of cancers, also known as malignancies, can lead to tumors, pain and death.

carcinogen  A substance, compound or other agent (such as radiation) that causes cancer.

neutron  A subatomic particle carrying no electric charge that is one of the basic pieces of matter. Neutrons belong to the family of particles known as hadrons.

nucleus  Plural is nuclei. (in biology) A dense structure present in many cells. Typically a single rounded structure encased within a membrane, the nucleus contains the genetic information. (in astronomy) The rocky body of a comet, sometimes carrying a jacket of ice or frozen gases. (in physics) The central core of an atom, containing most of its mass.

radioactive  An adjective that describes unstable elements, such as certain forms (isotopes) of uranium and plutonium. Such elements are said to be unstable because their nucleus sheds energy that is carried away by photons and/or and often one or more subatomic particles. This emission of energy is by a process known as radioactive decay.

radioactive decay  A process by which an element is converted into a lighter element through the shedding of subatomic particles (and energy).

subatomic  Anything smaller than an atom, which is the smallest bit of matter that has all the properties of whatever chemical element it is (like hydrogen, iron or calcium).

Bethany is the staff writer at Science News for Students. She has a Ph.D. in physiology and pharmacology from Wake Forest University School of Medicine.

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