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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 ×10 14 g/cm 3 ) - PowerPoint PPT Presentation

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Nuclear Chemistry

Nuclear ChemistryUnit 4Parts of an atom

RadiationIn this part of the unit, we will focus on the nucleus!Its very small (10-13 cm)

Its very dense (1.6 1014 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 ParticlesAlpha () particlesSlow moving nucleus of a helium atom.Not very dangerous, can be stopped bySkinA piece of paper

3 Main Types of Decay Particles

Beta ( ) ParticlesFaster moving electronsAre harmfulCan be stopped by wood or metal sheets

3 Main Types of Decay ParticlesGamma () ParticlesHigh-energy photon of lightVery dangerousPartially stopped by 6 inches of lead or 6 feet of concrete

FissionProcess of splitting a heavy nucleus into two more stable nuclei with smaller mass numbersReleases a lot of energy

FissionChain reactionWhen 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. . .

FissionCritical MassThe mass of material required to produce a chain reaction.

Fission: Where is it used?

Fission: Where is it used?Nuclear bombs

Nuclear Bomb Explosionhttp://www.youtube.com/watch?v=zsTRxXvQY0s

How fission bombs are madehttp://www.youtube.com/watch?v=fIbACkLU-38

Time-lapse video of all bombs explodinghttp://www.youtube.com/watch?v=_W_lLhBt8Vg

Fission: Where is it used?Nuclear submarines

Fission: Where is it used?Nuclear Imaging in medicineUses computers, detectors, & radioactive substances to look inside the human bodyPET Scan positron emission tomographySPECT scan single photon emission computed tomographyCardiovascular imagingBone scansTo detectTumorsAneurysms (weak spots in blood vessel walls)Irregular or inadequate blood flow to various tissuesBlood cell disorders & inadequate functioning of organs, such as the thyroidFission: Where is it used?PET Scan machine

Pet scan

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 40,000,000Fusion: 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?