Isotopes: Definition & Characteristics

Though John Dalton postulated that all atoms of an element are identical, scientists now know that isotopes, or different versions of each element, exist in nature. A Frayer Model is a perfect tool to deepen the understanding of isotopes. In this activity, students will define what isotopes are, illustrate important characteristics, and provide both examples and non-examples.

Isotopes are atoms of an element that differ in their number of neutrons. Because the identity of an atom is defined by its atomic number, as long as the atoms have the same number of protons, the atoms are the same element. Just as apples can be different sizes, atoms can also be heavy or light, even when they are the same element. Boron, for example, is found in nature as atoms with a relative mass of 10 amu (5 protons and 5 neutrons) or 11 amu (5 protons and 6 neutrons). In a sample of boron, around 20% of the atoms would have a mass of 10 amu and 80% would have a mass of 11 amu.

Extended Activity

Have students create a narrative storyboard or a timeline that illustrates the discovery of certain isotopes for a chosen element. Students should include the scientists involved and the process by which each isotope was discovered. This extension is a perfect way for students to further understand how continued research in science is constantly evolving things we already know.