Unit 4 Nuclear Chemistry

Parts of an atom

Radiation In this part of the unit, we will focus on the nucleus! It’s very small (10-13 cm) It’s very dense (1.6 ×14 g/cm3) A lot of energy holds it together! (millions of times more than involved in chemical reactions!)

Many nuclei are RADIOACTIVE! They spontaneously decompose or DECAY (break apart) forming a different nucleus & producing one or more particles

3 Main Types of Decay Particles Alpha (α) particles Slow moving nucleus of a helium atom. Not very dangerous, can be stopped by Skin A piece of paper

3 Main Types of Decay Particles Beta ( β) Particles Faster moving electrons Are harmful Can be stopped by wood or metal sheets

3 Main Types of Decay Particles Gamma (γ) Particles High-energy photon of light Very dangerous Partially stopped by 6 inches of lead or 6 feet of concrete

Fission Process of splitting a heavy nucleus into two more stable nuclei with smaller mass numbers Releases a lot of energy Leaves behind radioactive waste

Fission Chain reaction When you have a lot of a radioactive substance and the fission of one nucleus gives off particles that hit other nuclei that give off more particles that hit more nuclei. . .

Fission Critical Mass The mass of material required to produce a chain reaction.

Fission: Where is it used?

Fission: Where is it used? Nuclear bombs Nuclear Bomb Explosion http://www.youtube.com/watch?v=zsTRxXvQY0s How fission bombs are made http://www.youtube.com/watch?v=fIbACkLU-38 Time-lapse video of all bombs exploding http://www.youtube.com/watch?v=_W_lLhBt8Vg

Fission: Where is it used? Nuclear submarines

Fission: Where is it used? Nuclear Imaging in medicine To detect Uses computers, detectors, & radioactive substances to look inside the human body PET Scan – positron emission tomography SPECT scan – single photon emission computed tomography Cardiovascular imaging Bone scans Tumors Aneurysms (weak spots in blood vessel walls) Irregular or inadequate blood flow to various tissues Blood cell disorders & inadequate functioning of organs, such as the thyroid

Fission: Where is it used? PET Scan machine Pet scan

Radioactive Waste: What to do with it? Radioactive waste can be a solid, liquid, or gas. Depending on the source of the waste, it can last as long as a few hours or hundreds of thousands of years! Largest producer of radioactive waste is nuclear power plants

Waste at Chernobyl Farming in the area will be dangerous for at least 200 years! As for the reactor where the meltdown occurred… it will be at least 20,000 years before the area near it is safe to use.

Medical radioactive waste For example, you take radioactive iodine to treat hyperthyroidism, you can expect to give off radiation for 5-9 days after so there are precautions to take: Use separate towels and sheets than others. Wash them separately too! Use a special trash bag for your personal trash. After 80 days, this bag can be thrown out with other trash. Don’t cook for other people

Fusion Process of combining two light nuclei to form a heavier, more stable nucleus. Produces a lot more energy than fission! Is self-sustaining (chain –reaction) at more than 4,000,000° Does NOT leave radioactive waste behind

Fusion: Where is it used? Note: There are no PURE fusion bombs because of the extremely high temperatures needed to sustain a fusion chain reaction.

Fusion: Where is it used? Stars are powered by nuclear fusion in their cores. Small stars: The smallest stars only convert hydrogen into helium. Medium-sized stars (like our Sun): Late in their lives, when the hydrogen becomes depleted, stars like our Sun can convert helium into oxygen and carbon. Massive stars (greater than five times the mass of the Sun): When their hydrogen becomes depleted, high mass stars convert helium atoms into carbon and oxygen, followed by the fusion of carbon and oxygen into neon, sodium, magnesium, sulfur and silicon. Later reactions transform these elements into calcium, iron, nickel, chromium, copper and others. When these old, large stars with depleted cores supernova, they create heavy elements (all the natural elements heavier than iron) and spew them into space, forming the basis for life.

Fusion: Where is it used?