Presentation on theme: "Science Park HS -- Honors Chemistry The ABC's (or Alpha, Beta, Gamma) of Radioactivity."— Presentation transcript:
Science Park HS -- Honors Chemistry The ABC's (or Alpha, Beta, Gamma) of Radioactivity
Science Park HS -- Honors Chemistry Agenda Definition of Radioactivity and emissions Discussion of the three most important types of emissions What do we mean by half-life? Where is Radioactivity encountered? Is Radioactivity dangerous?
Science Park HS -- Honors Chemistry Expectations SWBAT state what radioactivity is, where these rays come from, what each ray is made of and state why they are dangerous. SWBAT identify 4 pioneer scientists who made important contributions to understanding radioactivity SWABT to explain the meaning of half-life. Student will be asked to find any sources of Radioactivity in his/her environment
Science Park HS -- Honors Chemistry 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
Science Park HS -- Honors Chemistry 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
Science Park HS -- Honors Chemistry Some Key Definitions Before We Move on Z = The Atomic Number. Its the Number of Protons in the nucleus of an Atom. Nucleus: Its where the Protons and Neutrons are located in an Atom. Protons: Positively Charged Particles in the Nucleus of the atom. Mass = (approx) 1 AMU Neutrons: Neutrally charged particles in the nucleus of an atom Mass = (approx) 1 AMU Mass Number of an atom: Number of Protons + Number of Neutrons in the nucleus of an atom.
Science Park HS -- Honors Chemistry The Nuclear Stability Belt
Science Park HS -- Honors Chemistry Kinds of Radioactivity The three main decays are Alpha, Beta and Gamma
Science Park HS -- Honors Chemistry Three Common Types of Radioactive Emissions Alpha Beta Gamma
An alpha particle is identical to that of a helium nucleus. It contains two protons and two neutrons. Alpha Decay
X A Z Y A - 4 Z He 4 2 Alpha Decay unstable atom more stable atom alpha particle
Alpha Decay Ra Rn He 4 2
X A Z Y A - 4 Z He 4 2 Ra Rn He 4 2 Alpha Decay
Rn He Po He 4 2 Rn Y A Z He 4 2 Alpha Decay
He 4 2 U Th He 4 2 X A Z + Th He 4 2 Alpha Decay
Th Y A Z He 4 2 Alpha Decay He Ra He 4 2 Th
X A Z + Pb He 4 2 Alpha Decay He Pb He 4 2 Po
Beta Decay A beta particle is a fast moving electron which is emitted from the nucleus of an atom undergoing radioactive decay. Beta decay occurs when a neutron changes into a proton and an electron.
Beta Decay As a result of beta decay, the nucleus has one less neutron, but one extra proton. The atomic number, Z, increases by 1 and the mass number, A, stays the same.
Beta Decay Po At
X A Z Y A Z Beta Decay Po Rn
Th Y A Z + 0 Beta Decay Th Pa
X A Z Pb Beta Decay Tl Pb
Bi Y A Z + 0 Beta Decay Bi Po
X A Z Bi Beta Decay Pb Bi
Science Park HS -- Honors Chemistry Three Common Types of Radioactive Emissions - Penetrability Alpha particles may be completely stopped by a sheet of paper, beta particles by aluminum shielding. Gamma rays, however, can only be reduced by much more substantial obstacles, such as a very thick piece of lead.
Science Park HS -- Honors Chemistry Another Contribution from Rutherford: Half-life of Radioactive Atoms The half-life of a radioactive substance, is the time required for one half of it to decay.
Science Park HS -- Honors Chemistry Sources of Radioactivity Primordial - from before the creation of the Earth Cosmogenic - formed as a result of cosmic ray interactions Human produced - enhanced or formed due to human actions (minor amounts compared to natural)
Science Park HS -- Honors Chemistry Where 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
Science Park HS -- Honors Chemistry Radioactivity – Is it a Health Problem? The Alpha, Beta and Gamma particles all add energy to the bodys tissues. The effect is called the Ionizing Energy. It can alter DNA. Even though Alpha particles are not very penetrative if the decaying atom is already in the body (inhalation, ingestion) they can cause trouble. The Time, Distance and Shielding principle
Science Park HS -- Honors Chemistry Radiation Exposure to Americans
Science Park HS -- Honors Chemistry Summary/Questions Name three of the science pioneers in the study of Radioactivity.? Why does a nucleus decay? Order these emissions from least to greatest penetrability: Gamma, Alpha, Beta. What is the greatest source of exposure to radioactivity in our everyday lives? If I tell you that that the half-life of Fellmanium-250 is 10 days, how much would be left after 30 days if I started with 1600 atoms?
Science Park HS -- Honors Chemistry Where to Get More Information htm EPA (Environmental Protection Agency) Dept of Energy