Science ObjectDigital resources are stored online in your NSTA Library.
Science Objects are two hour on-line interactive inquiry-based content modules that help teachers better understand the science content they teach. This Science Object is the second of three Science Objects in the Atomic Structure SciPack. It explores the structure-related properties that make one type of atom different from another, and looks more closely at the role of the neutron. The number of protons in the nucleus determines what an atom's electron configuration can be and so defines the element and its properties. An atom's electron configuration, particularly the outermost electrons, determines how the atom can interact with other atoms. Although neutrons have little effect on how an atom interacts with others, they do affect the mass and stability of the nucleus. The nucleus of radioactive isotopes is unstable and spontaneously decays, emitting particles and/or electromagnetic radiation. It cannot be predicted exactly when, if ever, an unstable nucleus will decay, but a large group of identical nuclei decay at a predictable rate. This predictability of decay rate allows radioactivity to be used for estimating the age of materials that contain radioactive substances.