Nuclear Chemistry Unit 10
Nuclear ChemistryUnit 10
RadioactivityThe spontaneous emission of
radiation by an unstable atomic nucleus.
DiscoveryHenri Becquerel-1896Worked with phosphorescent uranium
(thought to be x-rays)Marie and Pierre Curie were the one’s
to actually name the process as radioactivity
Nuclear Notation
Radioactive DecayAlpha Decay (α)Alpha particles are helium nuclei
consisting of 2 protons and 2 neutrons
Does not penetrate deeply into matter.
Loss of 2p and 2n results in the daughter atom being two elements before the parent atom.
Example:
Radioactive DecayBeta Decay (β)Beta particles are high energy
electrons with a -1 charge. Represented by e.
Pass through matter easier than alpha.The electron is produced when a
neutron turns into a proton and electron. Daughter atom has atomic number 1 greater than parent atom.
Example:
Radioactive DecayGamma Decay (γ)Gamma ray is a high energy form
of electromagnetic radiation without a mass or charge.
Need thick blocks of lead or concrete to stop.
Normally does not occur alone but accompanies other forms of decay.
PracticeDecay of U-238 to Pb-206: a,b,b,a,a,a,a,a,b,b,a,b,b,a
Detecting RadioactivityDetects ionizing radiation
Radioisotope DatingHalf-life – the time it takes for half of a given amount of a radioactive isotope to undergo decay.
Carbon-14 dating1 in a million carbon atoms Decays to nitrogen-14 after deathHalf life is 5,730 yearsOther isotopes used for datingPotassium-40 (half life = 1.25 billion years)Uranium-238 (4.5 billion years)Rubidium-87 (48 billion years)
Einstein and EnergyFirst scientist to realize the amount of potential energy available in matter.
E=mc2
E=Energy m = massc= speed of light (671,000,000 mph)
Nuclear FissionThe splitting of an atomic nucleus into two or more smaller fragments, accompanied by a large release of energy.
Uranium nuclei are split by bombarding with a neutron.
Nuclear FissionSubcritical mass – If there is not enough fissionable material present to sustain a chain reaction
(super)critical mass – If there is enough fissionable material to sustain a chain reaction. (exponential and dangerous if not controlled)
Nuclear Reactor
Elements UsedUranium-235 is the main radioactive element used in a fission reactor.
Plutonium-239 can also be usedBreeder reactionFission Bombs
Nuclear FusionProcess of combining two or more nuclei to form a larger nucleus.
Process that produces energy in stars.
Most typical fusion reaction is when hydrogen atoms fuse to make helium.
Fusion processDeuterium (D) – A hydrogen atom with a mass number of 2.Tritium (T) – A hydrogen atom with a mass of 3.
Radioisotopes and HealthTracers – used in the body to find abnormalities.Act like normal isotopesRadiation can be detected
Iron-59Used to show circulatory system
EnvironmentSulfur-35 used to trace pesticides from field
to streams
Sources of RadiationBackground radiation- caused by radioactive elements in rocks, fabrics, food, etc.
Health ProblemsRadiation can knock electrons
creating ions.Damages cell processesDividing cells pass down
damaged DNAWaste can take thousands of
years to decay
Measuring RadiationGray – equal to the
transfer of 1 joule of energy in the form of radiation to 1 kg of living cells.
Sievert (Sv)- equal to 1 gray multiplied by a factor that take tissue absorption into account.
Radon and the HomeRadon-222 can cause lung cancer.changes into isotopes of polonium and
lead.Po and Pb isotopes attach to dust
particles and enter lungs.Emit alpha particles which damage
cells.Radon is dense and normally
accumulates in basementsExhaust fan and sealing large cracks