Nuclear Nuclear ChemistryChemistry

Nuclear ReactionsNuclear Reactions

Nuclear chemistry is the Nuclear chemistry is the study of changes in an atom’s study of changes in an atom’s nucleus.nucleus.

Reactions that involve a Reactions that involve a change in the change in the nucleusnucleus of an of an atom are called atom are called nuclear nuclear reactionsreactions..

Characteristics of Nuclear ReactionsCharacteristics of Nuclear Reactions

Occur when nuclei emit particles and/or Occur when nuclei emit particles and/or raysrays

Atoms are often converted into atoms of Atoms are often converted into atoms of another elementanother element

May involve protons, neutrons, and May involve protons, neutrons, and electronselectrons

Associated with large energy changesAssociated with large energy changes Reaction rates aren’t normally affected by Reaction rates aren’t normally affected by

temperature, pressure, or catalysttemperature, pressure, or catalyst

What Causes Nuclear What Causes Nuclear Reactions?Reactions?

The nuclei of some atoms are The nuclei of some atoms are unstable and may undergo unstable and may undergo several changes.several changes.

Unstable systems gain Unstable systems gain stability by losing energy.stability by losing energy.

Certain atoms lose energy by Certain atoms lose energy by emitting rays and particles emitting rays and particles called called radiationradiation..

Related TermsRelated Terms

This spontaneous emission of radiation This spontaneous emission of radiation is a process called is a process called radioactivityradioactivity..

The process by which unstable nuclei The process by which unstable nuclei emit radiation to lose energy is called emit radiation to lose energy is called radioactive decayradioactive decay..

RadioisotopesRadioisotopes, isotopes of atoms , isotopes of atoms with unstable nuclei, undergo nuclear with unstable nuclei, undergo nuclear decay.decay.

Types of RadiationTypes of Radiation

AlphaAlpha

-Composed of alpha particles-Composed of alpha particles

-Contains 2p-Contains 2p++ and 2n⁰ and 2n⁰

--4422He or He or αα

BetaBeta

-Composed of beta particles-Composed of beta particles

-Fast moving e-Fast moving e--

- - 00-1-1ββ or or 00

-1-1ee

Types of Radiation (cont)Types of Radiation (cont) GammaGamma

-Not deflected by electric or -Not deflected by electric or magnetic fieldsmagnetic fields

-High energy electromagnetic -High energy electromagnetic radiation (not a particle)radiation (not a particle)

-No mass and No charge-No mass and No charge

--0000γγ

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Types of Radiation SummaryTypes of Radiation Summary

Type of Type of RadiationRadiation

SymbolSymbol ChargeCharge PenetratiPenetrationon

AbilityAbility

MassMass

alphaalpha 4422HeHe 2+2+ blocked by blocked by

paperpaperheaviestheaviest(4 amu)(4 amu)

betabeta 00-1-1ββ 1-1- blocked by blocked by

metal foilmetal foillightestlightest(1/1840 (1/1840 amu)amu)

gammagamma 0000γγ 00 not not

completely completely blocked by blocked by lead or lead or concreteconcrete

nonenone

Nuclear EquationsNuclear Equations

Used to express nuclear reactionsUsed to express nuclear reactions Both sides of the equation must have Both sides of the equation must have

an equal sum of atomic mass and an equal sum of atomic mass and atomic numbersatomic numbers

Examples:Examples:

2352359292U U 44

22He+ He+ 2312319090ThTh

37371919K K 00

-1-1ββ + + 37372020CaCa

41412020Ca Ca 4141

2020Ca + Ca + 00 00γγ

Half-LifeHalf-Life

The time required for one half of a The time required for one half of a radioisotope’s nuclei to decay into its radioisotope’s nuclei to decay into its products is called a products is called a half-lifehalf-life..

Amt Remaining=(Initial Amt)(1/2)Amt Remaining=(Initial Amt)(1/2)nn

-n = # half lives passed-n = # half lives passed Amt Remaining=(Initial Amt)(1/2)Amt Remaining=(Initial Amt)(1/2)t/Tt/T

-t=elapsed time-t=elapsed time

-T=duration of half life-T=duration of half life

Example half-life problems:Example half-life problems:

- How much of a 100.0g sample - How much of a 100.0g sample of of 198198Au is left after 8.10 days if its Au is left after 8.10 days if its half-life is 2.70 days?half-life is 2.70 days?

-A 50.0g sample of -A 50.0g sample of 1616N decays to N decays to 12.5g in 14.4 seconds. What is its 12.5g in 14.4 seconds. What is its half-life?half-life?

-The half-life of -The half-life of 4242K is 12.4hours. K is 12.4hours. How much of a 750g sample is left How much of a 750g sample is left after 62.0hours?after 62.0hours?

-What is the half-life of 99Tc if a -What is the half-life of 99Tc if a 500g sample decays to 62.5 g in 500g sample decays to 62.5 g in 639,000 years?639,000 years?

Fission and FusionFission and Fusion The splitting of an atoms nucleus into The splitting of an atoms nucleus into

fragments is called fragments is called fissionfission..

-Provides energy for nuclear power -Provides energy for nuclear power plantsplants

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The combining of atomic nuclei is called The combining of atomic nuclei is called fusionfusion..

-Fuels the sun-Fuels the sun http://www.visionlearning.com/library/http://www.visionlearning.com/library/

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