1. 10.4 Fission vs. Fusion Distinguish between fission and fusion

2. What is the strong nuclear force? The force that holds protons and neutrons together. The strong nuclear force is stronger than the repelling force of proton to proton. Works over a short distance

3. What makes a nucleus unstable? Neutrons help stability but too many or too few will make a nucleus unstable. Stable atoms have equal numbers of protons and neutrons >83 protons (the atomic number (bottom)) are always unstable. (b/c nuclear force can’t act over something so big) There are isotopes with less than 83 protons that are unstable b/c protons ≠ neutrons.

4. What is nuclear fission? The process by which a nucleus SPLITS into 2 or more smaller fragments, releasing neutrons and energy. Requires a neutron to start it going Large nucleus divides in to smaller nuclei Results in smaller total mass Missing mass is changed into lots of energy. Occurs uncontrolled in a nuclear bomb or controlled in a nuclear power plant (reactor)

5. How does a chain reaction happen? A nucleus splits when hit by neutrons This makes smaller nuclei that need less neutrons to be held together The extra neutrons are released and hit other large nuclei and those release neutrons that hit other nuclei that split and release neutrons and so on

6. Are chain reactions controllable? Yes by using materials that absorb neutrons. (control rods in a reactor block the neutrons)

7. What is fusion? When lighter nuclei COMBINE to make heavier nuclei Very hard to do Needs really hot temperatures Happens in stars (b/c of the heat and hydrogen available) Releases tons of energy as gamma rays Usually 4 hydrogen will make 1 helium in a multi-step process, but not the only type of fusion