1. Unit 4

3.  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 )  A lot of energy holds it together! (millions of times more than involved in chemical reactions!)

4.  They spontaneously decompose or DECAY (break apart)  forming a different nucleus & producing one or more particles

5.  Alpha (α) particles  Slow moving nucleus of a helium atom.  Not very dangerous, can be stopped by ▪ Skin ▪ A piece of paper

6.  Beta ( β) Particles  Faster moving electrons  Are harmful  Can be stopped by wood or metal sheets

7.  Gamma (γ) Particles  High-energy photon of light  Very dangerous  Partially stopped by 6 inches of lead or 6 feet of concrete

9.  Process of splitting a heavy nucleus into two more stable nuclei with smaller mass numbers  Releases a lot of energy

10.  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...

11.  Critical Mass  The mass of material required to produce a chain reaction.

13. NUCLEAR BOMBSNUCLEAR BOMB EXPLOSION  http://www.youtube.com/wat ch?v=zsTRxXvQY0s http://www.youtube.com/wat ch?v=zsTRxXvQY0s  How fission bombs are made  http://www.youtube.com/wat ch?v=fIbACkLU-38 http://www.youtube.com/wat ch?v=fIbACkLU-38  Time-lapse video of all bombs exploding  http://www.youtube.com/wat ch?v=_W_lLhBt8Vg http://www.youtube.com/wat ch?v=_W_lLhBt8Vg

14. NUCLEAR SUBMARINES

15. NUCLEAR IMAGING IN MEDICINE  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 TO DETECT  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

16. PET SCAN MACHINEPET SCAN

17.  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 40,000,000°

18. Note: There are no PURE fusion bombs because of the extremely high temperatures needed to sustain a fusion chain reaction.

19.  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.Sun  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.

21.  https://www.youtube.com/watch?v=neMEo8 ZrwuI https://www.youtube.com/watch?v=neMEo8 ZrwuI