Early Pioneers in Radioactivity _________: Discoverer of X-rays 1895 _________: Discoverer of Radioactivity 1896 __________: Discoverers of Radium and Polonium _________: Discoverer Alpha and Beta rays 1897 Burt, 2011

Isotopes….a review -mass of the atom depends on the number of _______and ________in the element -isotopes have different #s of ________ but same # of ____________(atomic #) ex. 12 C, 13 C, 14 C many isotopes have unstable nuclei and they release radiation (are radioactive)

Where are the Sources of Radioactivity? Naturally Occurring Sources: –Radon from the decay of _________ and Thorium –Potassium -40 – found in minerals and in plants –____________ – Found in Plants and Animal tissue Manmade Sources: –____________ use of Radioactive Isotopes –Certain Consumer products –(eg Smoke detectors) –Fallout from ___________ testing –Emissions from ___________ Power plants

Radioactivity- spontaneous decay of an unstable atomic nucleus accompanied by the emission of radiation. ________________ –An isotope of an element that undergoes radioactive decay ___________ nuclide (element)- unstable, higher energy element that decays into another nuclide ___________nuclide- stable product that results from this decay Ex. K 40 (parent) decays into Ar 40 (daughter element)

Types of radiation ________rays (α) - nuclear decay by emission of an alpha particle ( 4 He nucleus ). Click -easily blocked by clothing, paper, etc. _______rays (β)- Nuclear decay by emission of an electron click -can be stopped by thick wood; used in radiation therapy to kill cancer cells ________rays (γ)- emission of a high energy photon from the nucleus (like an X-ray) click -produced by radioactive decay; are a health hazard; maybe blocked by 6 in of cement

Three Common Types of Radioactive Emissions - Penetrability Alpha particles may be completely stopped by a sheet of _____________ Beta particles by ___________ shielding. Gamma rays can only be reduced by something such as a very thick piece of __________.

Half-life- time it takes for half of the atoms in a radioactive isotope to decay Each isotope has its own HL -half-life of 238 U is 4.5 billion years -half-life of 14 C is ______ years Decay continues until a ________, non-radioactive product is formed Decay of an individual atom is ___________

Half life - a geologic clock Half life - a geologic clock

Exponential Decay Decay of 226 Ra

___________Dating When a plant dies, it stops the intake of carbon Since the 14 C decays, after 5730 years, half of it will be gone We can just weigh a piece of dead wood, calculate how much 14 C it originally had and measure to how much it has now to get the age

__________ Dating We know the half -life of 238 U and 235 U They have series that end in 206 Pb and 207 Pb Compare how much U vs. special lead and calculate the age of the rock!! Carbon dating only good for about 50,000 years Uranium rock dating good for millions of years

Transmutations The changing of one element to another is called ________________________ This occurs whenever there is an alpha decay or a beta decay

Two Main Types of Nuclear Reactions ________ - two light nuclei are combined to form a heavier, more stable nucleus –This occurs in stars to produce energy (electromagnetic radiation) ______ - a heavy nucleus is split into 2 nuclei with smaller mass numbers –This occurs in nuclear power plants Burt, 2011

Nuclear Fusion Stars fuse __________________________ –Mass converts to energy Burt, 2011

Nuclear Fission Burt, 2011