Nuclear Chemistry – Day 3Nuclear Chemistry – Day 3
Welcome! Please pick up the practiceWelcome! Please pick up the practice
questions on half-lives. We will completequestions on half-lives. We will complete
this prior to the quiz.this prior to the quiz.
Turn in your honors intent letter today.Turn in your honors intent letter today.
Hmwk: Read Chapter 9 Section 2 and 3Hmwk: Read Chapter 9 Section 2 and 3
Test next Monday/TuesdayTest next Monday/Tuesday
Notebook check next timeNotebook check next time
Honors Proposal due next week.Honors Proposal due next week.
Complete the half-lives and radioactiveComplete the half-lives and radioactive
decay practice questions.decay practice questions.
Nuclear ForcesNuclear Forces
Protons and neutrons are tightly packed in theProtons and neutrons are tightly packed in the
Unstable nuclei undergo decay by emittingUnstable nuclei undergo decay by emitting
nuclear radiationnuclear radiation
An element can have both stable and unstableAn element can have both stable and unstable
The stability of a nucleus depends on theThe stability of a nucleus depends on the
nuclear forces that hold the nucleus together:nuclear forces that hold the nucleus together:
these forces act between the protons and thethese forces act between the protons and the
Why don’t the positively chargedWhy don’t the positively charged
protons repel each other ?protons repel each other ?
Strong nuclear forceStrong nuclear force: causes protons: causes protons
and neutrons to attract each other.and neutrons to attract each other.
This attraction is much stronger than theThis attraction is much stronger than the
electric repulsion between protonselectric repulsion between protons
Too many neutrons or protons canToo many neutrons or protons can
cause a nucleus to becomecause a nucleus to become
unstable and decayunstable and decay
Nuclei with more than 83 protons areNuclei with more than 83 protons are
always unstablealways unstable
These nuclei will always decay – releasingThese nuclei will always decay – releasing
large amounts of energy and nuclearlarge amounts of energy and nuclear
The decay results in a more stableThe decay results in a more stable
Nuclear FissionNuclear Fission
Fission: The process of splitting heavierFission: The process of splitting heavier
nuclei into lighter nuclei; the process bynuclei into lighter nuclei; the process by
which a nucleus splits into two or morewhich a nucleus splits into two or more
fragments and releases neutrons andfragments and releases neutrons and
Nuclear Fission – Video Clip
Nuclear Weapons: In fission
weapons, a mass of (
enriched uranium or plutonium) is
assembled into a supercritical mass
—the amount of material needed to
start an exponentially growing
nuclear chain reaction—either by
shooting one piece of subcritical
material into another, or by
compressing a subcritical mass with
chemical explosives, at which point
neutrons are injected and the
Nuclear Power Plants: Nuclear
energy is produced when a fissile
material, such as uranium-235
(235U), is concentrated such that
nuclear fission takes place in a
controlled chain reaction and
creates heat — which is used to boil
water, produce steam, and drive a
steam turbine. The turbine can be
Nuclear FusionNuclear Fusion
Fusion: the process in which light nucleiFusion: the process in which light nuclei
combine at extremely high temperatures,combine at extremely high temperatures,
forming heavier nuclei and releasingforming heavier nuclei and releasing
How the Sun shines
Nuclear fusion is the energy
source of stars – just like
our own Sun.
It has a nuclear fusion
reactor at its core.
The immense pressure and
a temperature of 16 million
degrees C force atomic
nuclei to fuse and liberate
About four million tons of
matter is converted into
sunlight every second.
Nuclear Radiation TodayNuclear Radiation Today
Nuclear radiation is all around you.Nuclear radiation is all around you.
Background radiationBackground radiation is the nuclearis the nuclear
radiation that arises naturally from cosmicradiation that arises naturally from cosmic
rays and from radioactive isotopes in therays and from radioactive isotopes in the
soil and air.soil and air.
Radiation is measured in units of rems.Radiation is measured in units of rems.
Exposure varies depending on locationExposure varies depending on location
and activities.and activities.
Beneficial Uses of NuclearBeneficial Uses of Nuclear
Smoke detectors – a small alpha-emittingSmoke detectors – a small alpha-emitting
isotope is used to detect smoke particlesisotope is used to detect smoke particles
in the air.in the air.
Disease detection – radioactive tracersDisease detection – radioactive tracers
are added to a substance so that itsare added to a substance so that its
distribution can be detected later. Thesedistribution can be detected later. These
are widely used in medicine.are widely used in medicine.
D:Ch0975459.htmlD:Ch0975459.html tracer cliptracer clip
Benefits continuedBenefits continued
Nuclear radiation therapy is used to treatNuclear radiation therapy is used to treat
Agriculture - radioactive tracers and radio-Agriculture - radioactive tracers and radio-
isotopes are used to help scientistsisotopes are used to help scientists
understand biological processes in plants.understand biological processes in plants.
MRI image of a healthy brainMRI image of a healthy brain
MRI image of a brain withMRI image of a brain with
Alzheimer’s DiseaseAlzheimer’s Disease
Possible Risks of Nuclear RadiationPossible Risks of Nuclear Radiation
Nuclear radiation can ionize atomsNuclear radiation can ionize atoms
Ionization is a change in the number ofIonization is a change in the number of
electrons in an atom or molecule, causing theelectrons in an atom or molecule, causing the
particle to be positively or negatively charged.particle to be positively or negatively charged.
Radiation sickness results from high levelsRadiation sickness results from high levels
of nuclear radiationof nuclear radiation
Studies have shown a relationship betweenStudies have shown a relationship between
high levels of radiation exposure and cancer.high levels of radiation exposure and cancer.
(Risk is determined by amount of exposure)(Risk is determined by amount of exposure)
Nuclear PowerNuclear Power
Nuclear fission is an alternative to fossilNuclear fission is an alternative to fossil
fuels as a source of energy.fuels as a source of energy.
Radioactive products of fission must beRadioactive products of fission must be
handled carefully and nuclear waste musthandled carefully and nuclear waste must
be safely stored.be safely stored.
Scientists are working on nuclear fusionScientists are working on nuclear fusion
reactors, but fusion reactions are difficultreactors, but fusion reactions are difficult
to produce in the laboratory.to produce in the laboratory.