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 decreases12 6

C 6 protons, 6 neutrons stable

14 6

C 6 protons, 8 neutrons unstable

Unstable Nucleus - Spontaneously decay into radioactive particles

ParticleParticle MassMass ChargeCharge SymbolSymbol Penetrating Penetrating powerpower

Alpha 4 Amu 2 + He α Low

Beta 0 amu 1- e β moderate

Positron 0 amu1 + e moderate

Gamma 0 amu none γ high

4 2

0 -1

0 +1

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+ chargedProton, positron, alpha Proton, positron, alpha particleparticle

- charged- chargedElectron (beta particle), Electron (beta particle),

neutralneutral

Neutrons, gamma Neutrons, gamma radiationradiation

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 + _________88 2

222

86Rn

86

Examples - Determine the missing nuclear particle

Now go back and label the reactions as alpha or beta decay

A. 210Pb --> ______ + 0e

B. 214Bi --> 214Po + _______

C. 214Po --> _________ + 210Pb

D. 206Tl --> 0 e + ________

82 -1

83 84

84 82

81 -1

210

83 Bi

0

-1 e4

2 He

206

82 Pb beta

alpha

beta

beta

Use chart N to determine the products of the following

A.

B.

85 Kr

232 Th

Beta decay0e-1

+36

85

37

Rb

Alpha decay4

2

He +90

228

88

Ra

1.Artificial Transmutation - 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. ReactionsIn 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 Ra88

222Rn + ________86

4He2

+9Be4

+ 1H1

6 Li3

4He2

Top number- Total number of protons and neutrons

Bottom number - Total number of protons

Natural Transmutations Only one reactant

Artificial Transmutations More than one reactant

Examples - Predict what particle or nucleus is missing

A. 27 Al + _______13

30P + 1n15 0

C. _______ + 2 H1

B. 6 Li + 1n 3 0

52Mn + 4He25 2

1

__________ + 3H

4He2

4He2

54Fe26

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

233U92

91Kr36

140Ba56

+ + EnergyEnergy

+ Energy+ Energy1n + 233 U --> 91Kr + 140Ba + 3 1n0 92 36 56 0

1n0

1n0

1n0

1n0

+

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 neutronsSince only one neutron is free, the energy released is constant

Controlled fission

Purpose To use the heat from a fission reaction to boil water

The boiling water turns a fan (turbine) which creates electricity

Fission Heat Steam Turn turbine ElectricityElectricity

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

RisksRisksExposureExposure

Too much exposure to radiation (accidental or on purpose) can cause

Serious illness or death

Mutations which can be passed on to future generations

DisposalDisposal

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 RespirationPhotosynthesis, Cell Respiration14C

18O

3H

14C6H12O614CO2

Diagnosis

131I Used to detect thyroid problems

99Tc 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.

TreatmentOther forms of radiation can be used to kill cancer cells

Cancer cells are killed easier by radiation than normal cells60Co

Expose tumor to radiation, it kills more cancer cells than normal cells

Radium

131I is also used to treat thyroid problems, as well as diagnose them.

Determining Age

When something is alive, it has a specific amount of 14C in itWhen it dies, the 14C undergoes half lives and decaysCount the number of half lives to determine the age (Carbon dating)

14C

238U

Very long half life

Measure the ratio of 238U to 206Pb 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 radiationRadiation is absorbed as it passes through different materials

Decays to 206Pb

Gamma radiation