25.2 25.2 –– Nuclear Decay Nuclear Decay
ObjectivesObjectives
Compare and contrast alpha, beta and Compare and contrast alpha, beta and gamma radiation.gamma radiation.
Define the half-life of a radioactive Define the half-life of a radioactive material.material.
Describe the process of radioactive dating.Describe the process of radioactive dating.
Nuclear RadiationNuclear Radiation
Particles and energy are Particles and energy are released from a decaying released from a decaying nucleusnucleus
http://abyss.uoregon.edu/~js/cosmo/lectures/lec07.html
Alpha particleAlpha particle
Two protons and Two protons and two neutrons two neutrons with an electric with an electric charge of +2charge of +2
Represented as Represented as a Helium a Helium moleculemolecule
Alpha ParticlesAlpha Particles
Leave charged ions in their Leave charged ions in their path when they travel through path when they travel through mattermatter
Least penetrating form of Least penetrating form of nuclear radiationnuclear radiation
Can cause serious biological Can cause serious biological damagedamage
http://library.thinkquest.org/3471/radiation_types_body.html
Smoke detectors give off alpha Smoke detectors give off alpha particles that ionize the surrounding airparticles that ionize the surrounding air
If smoke particles enter the ionized air, If smoke particles enter the ionized air, they will absorb the ions and electronsthey will absorb the ions and electrons
The circuit is broken and the alarm The circuit is broken and the alarm goes offgoes off
TransmutationTransmutation
Process of one element changing Process of one element changing to another through nuclear decayto another through nuclear decay
Beta particleBeta particleAn An electronelectron released released at high speed when a at high speed when a neutron decays into neutron decays into a protona proton
It is more penetrating It is more penetrating than alpha particlethan alpha particle
http://www.radfreenm.org/pages/radbasics.htm
http://www.physics.isu.edu/radinf/beta.htm
Gamma raysGamma rays
Penetrating Penetrating electromagnetic electromagnetic waves that carry waves that carry energy but have no energy but have no mass or chargemass or charge
Video Clip
http://library.thinkquest.org/3471/radiation_types_body.html
Start here 1Start here 1stst 5-1-13 5-1-13
http://w1.rso.utah.edu/train/basics.html
Half-lifeHalf-life
Is the length of time it takes half of the Is the length of time it takes half of the atoms of a sample of radioactive atoms of a sample of radioactive isotope to decayisotope to decay
Half-lives vary from fractions of a Half-lives vary from fractions of a second to billions of yearssecond to billions of years
Video Clip
http://www.regentsearth.com/Illustrated%20ESRT/Page%201%20(Radioactive%20Decay)/Radioactive%20Decay%20QuizMC.html
Radioactive isotopesRadioactive isotopes
Found in all rocks and minerals in Found in all rocks and minerals in varying amountsvarying amounts
Unstable & breakdown spontaneouslyUnstable & breakdown spontaneously
Radioactive decay occurs at a constant Radioactive decay occurs at a constant rate specific to each isotoperate specific to each isotope
Radioactive datingRadioactive dating
Carbon datingCarbon dating– Can be used to date once-living materialsCan be used to date once-living materials
Uranium datingUranium dating– Can be used to date rocksCan be used to date rocks
Radioactive decayRadioactive decay
When rocks form the amount of radioactive isotopes When rocks form the amount of radioactive isotopes is set and decay begins. is set and decay begins.
Radioactive isotopes break down into stable Radioactive isotopes break down into stable isotopes and the precise measurements of the isotopes and the precise measurements of the amount of stable vs. radioactive isotopes. The ratio amount of stable vs. radioactive isotopes. The ratio tells us how many years have passed since tells us how many years have passed since formation.formation.
Carbon-14 – all living things take in C-14, once they Carbon-14 – all living things take in C-14, once they die they stop taking in C-14. As fossils are dating, die they stop taking in C-14. As fossils are dating, the ratio of C-14 to stable carbon-12 is measured to the ratio of C-14 to stable carbon-12 is measured to determine how long ago the organism died.determine how long ago the organism died.
http://geomaps.wr.usgs.gov/parks/gtime/radiom.html
http://www.dlt.ncssm.edu/tiger/chem2.htm
In-Class Assignment/HomeworkIn-Class Assignment/Homework
25.2 Enrichment WKT25.2 Enrichment WKT
Key Terms WKTKey Terms WKT
Friday – Radioactivity LabFriday – Radioactivity Lab