Chapter 19 Nuclear Chemistry Marie Sklodowska Curie

Types of Nuclear Reactions

1. Radioactive Decay Emission of an alpha (  ) particle, beta (  ) particle, or gamma (  ) radiation  results in slightly lighter and more stable nuclei Emission of an alpha (  ) particle, beta (  ) particle, or gamma (  ) radiation  results in slightly lighter and more stable nuclei

2. Nuclear disintegration Nucleus bombarded with particles (e.g. ,p+, n 0 )  nucleus emits p + or n 0 and becomes more stable Nucleus bombarded with particles (e.g. ,p+, n 0 )  nucleus emits p + or n 0 and becomes more stable

3. Fission Very heavy nucleus splits to form medium mass nuclei Very heavy nucleus splits to form medium mass nuclei

4. Nuclear Fusion Light mass nuclei combine  form heavier, more stable nuclei Light mass nuclei combine  form heavier, more stable nuclei

Radioactivity Spontaneous disintegration of unstable nuclei   emitted Spontaneous disintegration of unstable nuclei   emitted e.g. U-238, radium (Ra-226) e.g. U-238, radium (Ra-226)

Types of radiation

Alpha (  ) Helium nucleus Helium nucleus 2 + chg. 2 + chg. Moves at 1/10 c Moves at 1/10 c Low penetrating power Low penetrating power

Beta (  ) Electrons Electrons 1- chg 1- chg Moves at close to c Moves at close to c 100x penetrating ability of  100x penetrating ability of 

Gamma (  ) Electromagnetic waves Electromagnetic waves 0 chg 0 chg Highest penetrating power Highest penetrating power

Half Life Time during which half of a given # of atoms of a radioactive isotope decays Time during which half of a given # of atoms of a radioactive isotope decays

Half Life example If you start with 7.0g of radioactive Radon-222 (half life = days) how many g remain after days? If you start with 7.0g of radioactive Radon-222 (half life = days) how many g remain after days? # half lives = time elapsed x 1 half life/ days # half lives = time elapsed x 1 half life/ days Original amt. of Radon-222 remaining x ½ for each half life = amt. of radon-222 remain. Original amt. of Radon-222 remaining x ½ for each half life = amt. of radon-222 remain. 

(cont.) 3 half lives = days x 1 half life/ days 3 half lives = days x 1 half life/ days 7.0g x ½ x ½ x ½ = 0.88 g Radon g x ½ x ½ x ½ = 0.88 g Radon-222

Properties of naturally occuring radioactive isotopes Expose film Expose film Produce electric chg. in surrounding air (Geiger counter) Produce electric chg. in surrounding air (Geiger counter)

properties (cont.) Cause fluorescence when mixed with certain cmpds Cause fluorescence when mixed with certain cmpds

Properties (cont.) Physiological effects Physiological effects e.g. medical treatments, killing bacteria e.g. medical treatments, killing bacteria

Properties (cont.) Decay Decay Radioactive isotopes decay into simpler atoms Radioactive isotopes decay into simpler atoms

Nuclear equations

Transuranium elements Elements with more than 92 protons Elements with more than 92 protons First two produced were neptunium and plutonium First two produced were neptunium and plutonium

Applications

1. Radioactive dating radioactive substances decay at known rates radioactive substances decay at known rates Rates are constant Rates are constant % parent v. daughter isotopes  age of material % parent v. daughter isotopes  age of material e.g. C-14 dating of ancient Egyptian lumber  ½ radiation of carbon in living trees, half life of carbon-14 is 5730 yrs., therefore lumber is 5700 yrs. old e.g. C-14 dating of ancient Egyptian lumber  ½ radiation of carbon in living trees, half life of carbon-14 is 5730 yrs., therefore lumber is 5700 yrs. old

2. Radioisotopes in medicine

3. Nuclear Power Plants Nuclear chain reaction Nuclear chain reaction

4. Nuclear Fusion ‘ultimate’ energy source ‘ultimate’ energy source Occurs in stars, e.g. the sun Occurs in stars, e.g. the sun 100,000,000 K temp 100,000,000 K temp