Drill – 10/19 How many grams of Cesium are 8.5x10 29 atoms?

Objectives SWBAT explain how some isotopes are made of unstable nuclei that decay over time emitting particles and energy. SWBAT define half-life and use it to determine the amount of radioactive decay products.

Intro to Nuclear Chemistry

Chemical Reactions Chemical Reactions involve only an atom’s electrons. The nucleus remains unchanged. Atoms of one element do not change into atoms of another element.

Nuclear Reactions Nuclear reactions involve a change in the atom’s nucleus. Atoms of one element do change into atoms of another element.

Radioactivity Radioactivity is a process where substances spontaneously emit radiation from their nucleus. Radioactive elements can change into atoms of another element by emitting radiation (rays or particles). does not require energy

Nuclear stability Why do atoms emit radiation?? Because their nuclei are unstable. What makes a nucleus unstable?? This can best be answered by looking at the role of the neutron.

We know what protons and electrons do… The number of protons identifies an element The electrons determine how reactive an element is What is the job of a neutron?

Neutrons hold the nucleus together Because like charges repel, the positive protons in a nucleus push away from each other Neutrons get in between the protons and act as glue, holding the nucleus in place

Nuclear stability Why do atoms emit radiation? Because their nuclei are unstable. The neutron-to-proton ratio determines an atom’s stability (either too many or too few neutrons). Unstable systems gain stability by losing energy.

Radioactive Decay Radioactive decay is when unstable nuclei lose energy by emitting radiation in a spontaneous process.

Half - life Half-lives are used to measure how fast radioisotopes (radioactive isotopes) decay Half-life is the amount of time for a sample to cut in half

Half-life Lab!