<<

10.2 Nuclear

• forces between and ______in the nuclei of • the stability of the nucleus depends on these forces

Strong Nuclear ­ holds protons (+) and (no charge) together

In a stable , the attractive forces are stronger than the repulsive forces, and the element does not undergo decay.

Too many neutrons or protons can cause a nucleus to become ______and ______.

Example: nuclei with > 83 protons are always unstable and decay REMEMBER, decay results in more stable nuclei.

1

Definition: process of splitting heavier nuclei into lighter nuclei

• During fission, both neutrons and are released.

Albert Einstein explained how matter can be converted into energy and energy into matter with his theory of relativity in 1905.

E = mc2

2 Chain Reactions (Fission)

Analogy: shooting marbles or dominoes

Neutron strikes a nuclei ­­> splits ­­> neutrons are emitted and strike other nuclei causing them to split

If every Uranium atom emits 2 neutrons when split, then these neutrons can split 2 more U atoms, which will produce more neutrons to split add'l atoms, etc.

3 This sounds like how Nuclear Reactors : a controlled chain reaction can be used to generate electricity by using the energy given off to heat water, which makes steam, which rotates a turbine to generate electricity.

Control rods are used to regulate fission by slowing down the chain reaction.

4 The Power of Fission

• U.S. receives about 20% of its power from plants.

• Around the world, there are 440 nuclear reactors that generate electriticy, > 400 that power ships and submarines, and a bit less than 300 that are used for research.

• France is the world's leader in using nuclear power for electricity (>75%).

5 Definition: combining light nuclei to form heavier nuclei.

• This process occurs in the sun (Hydrogen nuclei fuse to make Helium) and is used to make nuclear bombs. • A LOT of energy is needed to start a fusion reaction. • Major problem with fusion: must occur at VERY high temperatures (100's of millions of C).

http://www.cosmolearning.com/videos/fission­and­fusion/

6 7