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