Nuclear Chemistry

Reactions All the reactions you have see have involved transfer or share of electrons. The atoms on the left are the same as the atoms on the right; H 2 + O 2  H 2 O

Nuclear Reactions Atoms on the left are different from atoms on the right (but they may be the same). Atom A  Atom B + particle Atom A  Atom A + particle

Particles emitted in nuclear reactions are; alpha, beta, gamma NameSymbol Other nameChargeMass AlphaαHelium atom +2“4” Betaβelectron- 1“0” GammaγγPhoton He 0 e

What stops the particles Penetrative power

© 2009, Prentice-Hall, Inc. Charged particles are deflected The three types of radiation were discovered by Ernest Rutherford: –  particles –  particles –  rays

Isotopes of carbon reminder Isotopes are atoms of the same element with different masses. The different masses are due to the different numbers of neutrons C 12 6 C 13 6 C 14 6 C Neutrons

Calculating number of neutrons of Isotopes Isotopes are atoms that differ in the number of neutrons. Number of neutrons = Mass number – Protons Carbon CNeutrons = = 6 Carbon CNeutrons = = 8 Number of protons = Atomic number. See Periodic Table

Nuclear reaction - Beta decay Carbon-14 is unstable and decays to the more stable atom Nitrogen-14  e 14 6 C 14 7 N

Nuclear reaction - Beta decay

This is background information. Not required in testing.

Alpha decay

Nuclear reaction - Alpha decay Uranium-238 is unstable and decays to the more stable isotope Thorium-234.  U Th 4242 He 238 – 234 = 4 Mass difference92 – 90 = 2 Number of protons difference

Nuclear Fusion Fusion = bring together From two small a larger one is formed. Huge amount of energy is produced. Most of the energy given off by the Sun is produced by a process involving the fusion of hydrogen nuclei.

Nuclear Fission Fission = Break apart From one large one, two smaller are formed Huge amount of energy is produced.

Half Life Try these simulations; half life half life Nuclear decay is measured in terms of half life. The half life of an isotopic atom is the time it takes for half of the atoms to decay to another atom. Iodine-131 has a half life of 8 days. A sample of 1 mg of Iodine today will decay to 0.5 mg of Xenon after 8 days, 0.5 mg of Iodine-131 are left.

Half life examples Carbon-14 half life is 5,000 years. How long will it take for 100 gram of carbon-14 to decay to a value less than 10 gram? A. 20,000 years 100 g 0 years 50 g5,000 years 25 g10,000 years 12.5 g15,000 years 6.25 g20,000 years

Half life examples Technetium-99m half life is 6 hours (h) How much of the 500 gram Tc-99 will remain after one day? A: g 500 g 0 h 250 g6 h 125 g12 h 62.5 g18 h g24 h