Transmutation- When the nucleus of one element changes to the nucleus of another Stability- Most elements are very stable - Those above atomic number 83 are not and are radioactive - Are known as radioisotopes - Instability is related to the ratio of protons to neutrons - As the number of neutrons to proton gets above 1.5 : 1.0 the stability decreases 12 6 C 6 protons, 6 neutronsstable 14 6 C 6 protons, 8 neutronsunstable

Unstable Nucleus- Spontaneously decay into radioactive particles ParticleMassChargeSymbol Penetrating power Alpha4 Amu2 + He α Low Beta0 amu1- e β moderate Positron0 amu 1 + e moderate Gamma0 amunone γ high Radioactive Particles

You can determine which particles are given off in some cases by observing how the particle reacts in an electric field Radiation source A positively charged particle willbend toward the negative plate A negatively charged particle willbend toward the positive plate A neutral particle willnot bend toward either plate + charged Proton, positron, alpha particle - charged Electron (beta particle), neutral Neutrons, gamma radiation

Alpha Decay – a Helium nucleus is given off * Atomic number decreases by 2 * Number of protons decreases by 2 * Number of neutrons decreases by 2 * Mass number decreases by 4 Natural Transmutation – occurs because of high neutron to proton ratio - Decay particles are found in products

Beta Decay - Actually it is an electron 0 -1 e No noticeable mass Opposite charge of a proton  * Atomic number increases by 1 * Number of protons increases by 1 * Number of neutrons decreases by 1 * Mass number remains the same

Positron Emission * A proton is converted into a neutron * Atomic number goes down 1 * Mass number stays the same * Number of protons goes down by 1

Balancing Nuclear Equations - Mass and charge must balance on both sides of equation 226 Ra --> 4 He + _________ Rn 86 Examples - Determine the missing nuclear particle Now go back and label the reactions as alpha or beta decay A. 210 Pb --> ______ + 0 e B. 214 Bi --> 214 Po + _______ C. 214 Po --> _________ Pb D. 206 Tl --> 0 e + ________ Bi 0 -1 e 4 2 He Pb beta alpha beta

Use chart N to determine the products of the following A. B. 85 Kr 232 Th Beta decay 0e0e Rb Alpha decay 4242 He Ra

1.Artificial Transmutation - Process of bombarding a stable nucleus with accelerated particles - Speed up subatomic particles and hit them against nuclei - Always has two reactants one which is a particle from Table O

C. Writing Nuclear Reactions 1. Reactions In natural transmutations, we always made sure we had conservation of mass The same applies to artificial transmutations, only now we have at least two reactants 226 Ra Rn + ________ 86 4 He Be H 1 6 Li 3 4 He 2 Top number-Total number of protons and neutrons Bottom number -Total number of protons Natural TransmutationsOnly one reactant Artificial Transmutations More than one reactant

Examples - Predict what particle or nucleus is missing A. 27 Al + _______ P + 1 n 150 C. _______ + 2 H 1 B. 6 Li + 1 n Mn + 4 He __________ + 3 H 4 He Fe 26

Nuclear Fission One type of artificial transmutation -Splitting of a large nucleus into two or more smaller nuclei -Used in nuclear reactors and bombs -Small nuclei are too stable to be split -A small amount of mass is lost and converted to energy.

Reaction Usually, a large nucleus is hit by a slow moving neutron 233 U Kr Ba Energy + Energy 1 n U --> 91 Kr Ba n n1n 0 1n1n 0 1n1n 0 1n1n 0 + Notice -When the uranium splits, it releases three more neutrons These can hit three more uranium nuclei

Use a CONTROLLED fission reaction to produce electric energy Not a chain reaction Chain reaction We release more energy at each step In a controlled reaction, we must remove some neutrons to keep the reaction constant Material absorbs neutrons Since only one neutron is free, the energy released is constant Controlled fission

PurposeTo use the heat from a fission reaction to boil water The boiling water turns a fan (turbine) which creates electricity FissionHeatSteamTurn turbine Electricity Purpose of a Nuclear Reactor

Fusion -Combine light nuclei to make larger ones - Happens on the sun - Requires extreme temperatures and pressures

Half - Life - The time it takes for half of the atoms in a given sample of an element to decay -Each isotope has its own ½ life - Table N shows ½ life for various isotopes - Once one ½ life has taken place only ½ the original amount of the isotope will be found - Table N last box gives info for determining half life

Risks and Uses of Radioactive Substances Risks Exposure Too much exposure to radiation (accidental or on purpose) can cause Serious illness or death Mutations which can be passed on to future generations Disposal Some radioactive waste can last for thousands of years. Currently running out of room to store the waste Power plants

Accident Accidental release of radiation or radioactive waste can be very damaging to people and the environment. Chernobyl Tracers Use to follow chemicals through complex reactions Photosynthesis, Cell Respiration 14 C 18 O 3H3H 14 C 6 H 12 O 6 14 CO 2

Diagnosis 131 I Used to detect thyroid problems 99 Tc Used to detect brain tumors Ba Used to detect intestinal problems Inject isotope into a person to detect an illness Use isotopes with low radioactivity, short half lives and quickly eliminated from the body.

Treatment Other forms of radiation can be used to kill cancer cells Cancer cells are killed easier by radiation than normal cells 60 Co Expose tumor to radiation, it kills more cancer cells than normal cells Radium 131 I is also used to treat thyroid problems, as well as diagnose them.

Determining Age When something is alive, it has a specific amount of 14 C in it When it dies, the 14 C undergoes half lives and decays Count the number of half lives to determine the age (Carbon dating) 14 C 238 U Very long half life Measure the ratio of 238 U to 206 Pb in rocks to determine their age. Sterilization Some foods or materials are exposed to radiation to kill bacteria and molds Measurement Can measure thickness of substances very accurately using radiation Radiation is absorbed as it passes through different materials Decays to 206 Pb Gamma radiation