Nuclear Fission Nuclear Fusion Warm up Carbon10 and

Nuclear Fission & Nuclear Fusion Warm up: Carbon-10 and Carbon 9 are what in relation to each other and how are they different?

Forces • What holds an atom together? • Why doesn’t the nucleus of an atom fly apart if it’s made of positively charged protons?

Forces • Strong Nuclear Forces hold the nucleus of an atom together. • Placement of neutrons spaces protons apart JUST enough to help keep everything stable

Who discovered radioactivity? • In 1896, Henri Becquerel accidentally left pieces of uranium salt in a drawer on a photographic plate. When he developed the plate, he saw an outline of the uranium salt on it. He realized that it must have given off rays that darkened the film.

Who discovered radioactivity? • Two years later Marie and Pierre Curie discovered two new elements, Polonium and Radium, both radioactive.

Radioactive Elements • Any element over atomic number 83 is radioactive. • Radioactive materials have unstable nuclei (too few or too many neutrons). • When an unstable nucleus decays, it breaks apart emitting particles and energy as it decays.

Nuclear reactions • There are two main types of nuclear reactions: – Nuclear fission – Nuclear fusion A series of fission reactions is called a chain reaction.

Fission • Definition: The process used to release nuclear energy by splitting a nuclei •

What nuclei can split during nuclear fission? • Only large nuclei like U or plutonium can split apart during nuclear fission. • The idea is that a neutron will collide with an atom that is already unstable causing it to split into two stable atoms • This process releases energy and excess neutrons

Nuclear Power • Nuclear power plants use fission to produce energy. • Nuclear power plants are used in many countries (France is the leader). • Calvert cliffs nuclear power plant (55 miles away) Take this quiz to test your fear of nuclear power plants. Should you fear?

Fusion • The sun is powered by nuclear fusion. – THE SUN IS A STAR! • In a nuclear fusion reaction, two small, light nuclei combine to form one larger, heavier nucleus. • Two hydrogen atoms combine under extreme heat and pressure to form a helium atom.

Fusion • Why can’t we use the fusion reaction in nuclear power plants? 1. needs lots of energy 2. need to overcome electrical forces 3. difficult to control 4. never been produced in a nuclear power plant

WHY DO WE CARE ABOUT FUSION IF WE CANT USE IT YET?

Fusion on the Sun • The heat & light Earth receives comes from this process. • About 1% of the Sun’s hydrogen has been changed into energy. • Sun has enough H to continue fusion reactions for another 5 billion years.