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Nuclear Chemistry

Nuclear Chemistry. Chapter 21.1 Page 680. The Nucleus. The atomic nuclei are made up of… Protons Neutrons These are collectively called nucleons Recall we represent the relative numbers of protons and neutrons a nuclide for an atom ( 6 12 C)

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Nuclear Chemistry

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  1. Nuclear Chemistry Chapter 21.1 Page 680

  2. The Nucleus • The atomic nuclei are made up of… • Protons • Neutrons • These are collectively called nucleons • Recall we represent the relative numbers of protons and neutrons a nuclide for an atom ( 612C) • And an atom with varying number of neutrons is called an isotope.

  3. Nuclides can be represented 2 ways • 228Ra, the superscript is the mass 88 number (Protons and neutrons) and subscript is the atomic number ( # of Protons) 2. Ra-228, where the atomic number if place after a hyphen.

  4. Mass defect • You would assume that atoms are neat, orderly, packages where the number of electron equals the number of protons. And the number of proton would equal the number of neutrons. (and then the mass of positive and negative charges would be equal) • This is not always so…… • The difference between the mass of the atom and the mass of the sum of an atoms protons, neutrons, and electrons is called its mass defect

  5. Illustration of Mass defect • Let’s consider Li-7 • 3 protons: (3 x 1.007276 amu) = • 4 neutrons: (4 x 1.008665 amu) = • 3 electrons: (3 x 0.0005486 amu) = • Total combined mass: 7.0581338amu • but the laboratory measured mass of the Lithium atom is 6.941 amu • A difference of 0.1171338 amu • What is the cause of the loss of mass? • Isn’t mass conserved (some kind of law right)?

  6. Answer- Energy!!! • I bet you’ve heard of e=mc2!!!!! • In Einstein’s famous equation • energy can equal mass • Mass can equal energy • The mass lost in the formation of the atomic nuclei is converted into ENERGY!!!!

  7. Were does this energy go? • The sun!!.... An endless supply of nuclear energy • This type of energy is called FUSION • It reaches Earth in the form of radiation • UVA • UVB • Wear your sunscreen…

  8. Practice problems • Turn in lab • Demonstration of nuclear fusion • HW: Hand-out: Mass Decay 1-8

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