Early Pioneers in Radioactivity Roentgen: Discoverer of X-rays 1895 Becquerel: Discoverer of Radioactivity 1896 The Curies: Discoverers of Radium and Polonium Rutherford: Discoverer Alpha and Beta rays 1897

Radioactive Bands The Firm- “Radioactive” circa 1985Radioactive Imagine Dragons- “Radioactive” circa 2012Radioactive

What do we mean by Radioactivity? Radioactive decay is the process in which an unstable atomic nucleus loses energy by emitting radiation in the form of particles or electromagnetic waves. There are numerous types of radioactive decay. The general idea: An unstable nucleus releases energy to become more stable Decay continues until a stable, non-radioactive product is formed

Reason for Radioactivity The number of Neutrons in the nucleus affects the stability of the atom In some cases all the isotopes are unstable

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

What are the Sources of Radioactivity? Naturally Occurring Sources: –Radon from the decay of Uranium and Thorium –Potassium -40 – found in minerals and in plants –Carbon 14 – Found in Plants and Animal tissue Manmade Sources: –Medical use of Radioactive Isotopes –Certain Consumer products –(eg Smoke detectors) –Fallout from nuclear testing –Emissions from Nuclear Power plants

Products of Radioactive Decay When the unstable element (Parent Isotope) decays it makes: – a new element (Daughter Element) –Gives off radiation U 4 2 He Th ParentradiationDaughter

Three Common Types of Radioactive Emissions Alpha Beta Gamma

Half-life- time it takes for half of the atoms in a radioactive isotope to decay Each isotope has its own HL HL cannot be altered by temperature or pressure Decay continues until a stable, non-radioactive product is formed Decay of an individual atom is random

Half life – exponential decay Half life – exponential decay

Carbon 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

Uranium 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

Telling time by absolute age Carbon-14 to Nitrogen 14 in ~5700 years found in any living thing Uranium-235 to lead 207 in 700 million years Potassium-40 to Argon-40 in 1.3 billion years found in the mineral feldspar Uranium-238 to lead 206 in 4.5 billion years Thorium 232 to Lead 208 in 14 billion years. Rubidium 87 Strontium 87 in 48.6 billion years

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

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

Nuclear Power Plant Fission of Uranium in the reactor creates large amounts of energy to heat water, spin a turbine and generate electricity