Nuclear Chemistry Unit

January 28th HW Due Thurs. 1/30 Read pages 284 291 Define: Radioactivity Nuclear Radiation Alpha Particle Beta Particle Gamma Ray Half-Life Answer: -Questions 1-3 -Write the symbols for alpha, beta and gamma. -What do these symbols come from? -Write the nuclear decay reactions for - Alpha decay Ra (page 287) Beta decay C (page 287) -What is the half life of Iodine 131? -What is the half life of carbon 14? -What is the half life of Uranium 235?

Forms of Energy The five main forms of energy are: Heat Chemical Electromagnetic Nuclear Mechanical

Nuclear Radiation Many elements can change through radioactivity. -Radioactive elements have unstable nuclei. -Radioactive elements can decay. Emit radiation Can become a different isotope of the same element Can become a different element!

Alpha Particle Types of Radiation Helium nucleus with a + 2 charge The largest radioactive particle Don t penetrate very deep Beta Particle A fast moving electron -1 charge Can travel through paper, but wood or aluminum will stop it. Gamma Particle Tiny and too small to measure (like photons) No charge Travel through clothes and even walls

Alpha decay Alpha particle has a mass of 4. -- 2 protons and 2 neutrons --Mass goes down by 4 --Atomic # goes down by 2 7

Beta decay Beta particle has an tiny mass. -- A neutron is converted to a proton --Mass stays the same --Atomic # goes up by 1 234 Th 234 Pa + 0 e 90 91 1 beta particle 8

Gamma radiation No change in atomic or mass number 11 B 11 B + 0 γ 5 5 0 boron atom in a high-energy state 9

Temperature, pressure, concentration, and catalysts affect reaction rates Temperature, pressure, and catalysts do not normally affect reaction rates Comparison of Chemical and Nuclear Reactions Chemical Reactions Occur when bonds are broken or formed Involve only valence electrons Associated with small energy changes Atoms keeps same identity although they may gain, lose, or share electrons, and form new substances Nuclear Reactions Occur when nuclei combine, split, & emit radiation Can involve protons, neutrons, & electrons Associated with large energy changes Atoms of one element are often converted into atoms of another element

Radiation Composition & Symbol Is shielded or stopped by? Alpha 2 p+ and 2 n 0 paper Beta Stream of high speed e- Clothing, wood Gamma Very high energy electromagnetic radiation Concrete, lead

Nuclear Fission A heavy nucleus splits into more stable nuclei of intermediate mass.

Little Boy and Fat Man

Atomic Bombs Atomic bombs are an example of Fission Reactions. Little boy and Fat man were Atomic bombs made from fission reactions with uranium and plutonium respectively. A fission chain reaction is started and continues until the bomb destroys itself.

Nuclear Fusion Low-mass nuclei combine to form a heavier, more stable nucleus.

Hydrogen Bombs Hydrogen bombs are an example of nuclear fusion. Two isotopes of hydrogen, 2 H and 3 H, fuse together and produce a lot of energy in the process. H-bombs release significantly more energy than atomic bombs.

The Sun: Nuclear Fusion Sun + + 4 H Four hydrogen nuclei (protons) 2 e Two beta particles (electrons) He 1 0 4 + 1-1 2 + Energy One helium nucleus

Comparing Fission and Fusion http://media-1.w eb.britannica.com/eb-media/03/72203-035-4d92bdbc.jpg

Nuclear Fission Nuclear Fusion

Nuclear Fission Nuclear Fusion A heavy atom splits into two or more lighter nuclei Ex: Atomic Bombs & Nuclear reactors Release huge amounts of energy Produce nuclear waste High temp and pressure are used to combine light atoms to make heavier atoms Ex: Fuels the sun and stars & Hydrogen Bombs

map: Nuclear Energy Insti tute Nuclear Power Plants

Nuclear Power Plants Uranium-235 undergoes nuclear fission and releases thermal (heat) energy. This turns water to steam which spins turbines. The turbines produce electrical energy. Nuclear waste is fuel rods with unreacted uranium and radioactive products of fission. Right now this waste is buried in waste management facilities, like Yucca Mountain.

http://www.ambrosevideo.com/resources/documents/89.jpg Did You Know?

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Half-Life The time needed for one-half of the nuclei in a radioisotope to decay and emit their radiation to form a different isotope Half-time emitted Uranium 235 710 million yrs alpha, gamma Plutonium 239 24.000 yrs alpha, gamma During operation, nuclear power plants produce radioactive wastes, including some that remain dangerous for tens of thousands of years www.bio.miami.edu/beck/esc101/chapter14&15.ppt

Relative Doses from Radiation Sources cstl-cst.semo.edu/bornstein/bs105/ Energy%20Use%20-%203.ppt

Effects of Radiation Genetic damages: from mutations that alter genes Genetic defects can become apparent in the next generation Cellular damages: to tissue, such as burns, miscarriages & cancers

The nucleus of an atom is the source of nuclear energy. Nuclear Energy

Nuclear Energy When the nucleus splits (fission), nuclear energy is released in the form of heat energy and light energy. Nuclear energy is also released when nuclei collide at high speeds and join (fuse).

Locations of Facilities Source: http://www.pbs.org/wgbh/amex/three/maps/index.html