1. Isotopes

2. From the periodic table – What number equals the number of protons? • Atomic Number

3. From the periodic table – How is the mass of a “regular” (most abundant) atom determined? • Protons + Neutrons = Atomic Mass

4. An Isotope is defined as… • An Atom of an Element that has the same number of protons as another atom of the same element but a different number of neutrons.

5. The element hydrogen, for example, has three commonly known isotopes: protium, deuterium and tritium.

6. Since the atom has the same protons Isotopes of an element have the same chemical properties.

7. Lithium

8. One way to write the isotope

9. Another way to write the isotope Na - 23

10. Why are the masses on the periodic table decimal numbers? Average of all the isotopes of that element

11. If an atom has a Different number of neutrons • May make the element have a differentradioactivity. • Radioactivity is the release of energy and matter that results from changes in the nucleus of an atom • An isotope that is radioactive is called a radioisotope or radionuclide. The

12. Radioactive Isotopes Often called Radioisotopes How does this happen? An additional neutron or two may upset the nucleus and cause the atom to become unstable. In an unstable atom, the nucleus changes by giving off a neutron to get back to a balanced state. As the unstable nucleus changes, it gives off radiation and is said to be radioactive.

13. Elements with atomic # greater than 83 • Are Radioisotopes • Have unstable nuclei and are radioactive.

14. Elements with atomic # greater than 83 and less Have isotopes with a stable nucleus And Most have at least one radioisotope with an unstable nucleus.