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Unit 2 Part 2: Nuclear Chemistry
1st, 3rd, and 4th Periods
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Nuclear Chemistry Nuclear chemistry is the study of the structure of atomic nuclei and the changes they undergo. Why would the nucleus want to undergo a change? TO BECOME MORE STABLE & HAVE LESS ENERGY!!!
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Radioactivity – The Beginning
In 1896, Antoine Becquerel and his graduate students, Marie and Pierre Curie, discover radioactivity They used Uranium salts which were placed next to film plates. When opened, the plates were found to be developed.
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The Curies showed that uranium gave off rays that caused the plates to become exposed
Rays were called radioactivity The three won a Nobel Prize for their work
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This work was a deathblow to the theory of an indivisible atom
Relation to Dalton This work was a deathblow to the theory of an indivisible atom Radioactive isotopes have unstable nuclei that overtime transform to a stable non- radioactive nucleus
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Three types of radiation are produced: alpha, beta and gamma particles
Radioactive Decay Radioactive Decay-process in which an unstable nucleus loses energy by emitting radiation Three types of radiation are produced: alpha, beta and gamma particles
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Alpha Radiation () Helium nuclei emitted from a radioactive source Alpha particles- two protons and two neutrons; double positive charge Written as 42He
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Safety Concerns Because of large mass and charge, these are not very penetrating Can be stopped by a sheet of paper or even dead skin cells Harmful if ingested
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Alpha Particle Loss of alpha particle lowers atomic number by two and mass number by four Ex: Uranium-238 decays to Thorium- 234 and an alpha particle 238 92U Th + 42He
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Beta Radiation ( ) Formed by the decomposition of a neutron of an atom 10n 11H + 0–1e Beta particles- fast moving electrons
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Safety Concerns Contain half the charge and are much lighter than alpha particle Much more penetrating Can be stopped by aluminum foil or thin pieces of wood
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Beta Particles Written as 0–1e or 0–1 The proton stays in the nucleus and the electron is ejected from the atom Ex: Carbon-14 decays to Nitrogen-14 and a beta particle 146C 147N + 0–1e
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Gamma Radiation ( ) Electromagnetic (EM) Radiation Visible light is also EM radiation, but at a much lower energy Often emitted by the nuclei of disintegrating radioactive atoms along with alpha and beta radiation
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Gamma Rays No mass and no electrical charge Does not alter atomic number or the mass number of an atom This type of radiation only releases energy from the nucleus Symbol: (gamma)
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X-Rays X-Rays are NOT emitted during radioactive decay Produced when excited electrons in certain metals lose their energy
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Except for their origins, gamma and x- rays are essentially the same
Both rays pass easily through paper, wood, and the human body Can be mostly stopped by several meters of concrete or several centimeters of lead
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Positron: a positively charged electron; 0+1e or 0+1 Neutron: 10n0
Nuclear Equations Other Particles: Positron: a positively charged electron; 0+1e or 0+1 Neutron: 10n0 Proton: 11p+ or 11H+
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