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Chapter 2 - Atoms,MoleculesandIons Chapter2(...

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8/26/2011 1 Atoms, Molecules and Ions Chapter 2 (Students are responsible for reading units 2.1 2.2) What are the Goals (Chapter 2)? Understand what an atom is. Understand the structure of an atom . Learn what atomic weights are. Introduce the periodic table and some basic information it includes Learn the relationship between atoms, elements, compounds and molecules. Learn what ions are, what ionic compounds are and how they are named. Introduce what organic chemistry and organic molecules are.
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8/26/2011 2 http://www.udel.edu/chem/white/C647/Penicillin.gif Penicillin Where are the atoms in this representation of a compound? In this drawing, what do the different colors mean? Is this an ionic compound or an organic molecule? Chemical Composition of the World: Atoms 101  “indivisible, uncuttable” All matter is composed of atoms which cannot be further split into smaller portions Atoms are completely solid Atoms are homogeneous, with no internal structure Between atoms there is empty space Atoms differ in size Democritus ( c .460 c .370 B.C.)
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8/26/2011 3 John Dalton (1766 1844) Chemical Composition of the World: Atoms 200 Each element is composed of extremely small particles called atoms. All atoms of a given element are identical to one another in mass and other properties, but the atoms of one element are different from the atoms of other elements. The atoms of one element cannot be changed into atoms of a different element by chemical reactions; atoms are neither created or destroyed in chemical reactions. Compounds are formed when atoms of more than one element combine; a given compound always has the same relative number and kind of atoms.
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8/26/2011 4 Chemical Composition of the World: Atoms 300 Thomson’s “plum pudding” model Electrons embedded in a shell of positive charge Rutherford’s model Electrons randomly circulating around nucleus made of protons Rutherford’s Experiment – How does it support his hypothesis for atomic structure rather than Thomson’s?
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8/26/2011 5 The Modern Atom Most of the atom is empty space. Atomic radius = ~ 10 10 m Nuclear radius = ~ 10 15 m Volume ratio: V Atom : V Nucleus = ~ 10 15 Au foil Atoms, Molecules and Ions The Modern Atom The atom is made up of three fundamental particles: The proton , p + The neutron , n 0 The electron , e Nearly all of the mass of the atom is contained in the nucleus Nucleus } Nuclear
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8/26/2011 6 Atoms, Molecules and Ions The Modern Atom proton neutron electron Mass/ kg 1.67x10 27 1.675x10 27 9.1x10 31 Charge* +1 0 1 Location Nucleus Nucleus Atom Stability Stable Unstable Stable outside the nucleus * In units of 1.6 x 10 19 C Atoms, Molecules and Ions The Modern Atom Structure A Small Dense Nucleus Nuclear Radius: ~ 10 15 m (1 fm) Density of the nucleus: ~ 100,000,000,000,000 g cm 3 (Density of water = 1 g cm 3 ) The mass of the electron is ~ 1/2000 that of the proton and neutron – most of the mass of the atom is in the nucleus
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8/26/2011 7 Atoms, Molecules and Ions The Four Forces of Nature
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