Ochem_UNIT_2 - OCHEMUNIT2:STRUCTUREANDBONDING A...

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OCHEM   UNIT 2: STRUCTURE AND BONDING A. ATOMIC STRUCTURE: A REVIEW 1. MODERN VIEW ON THE MICROSCOPIC STRUCTURE OF  MATTER 2. SOME DEFINITIONS atomic number (Z)  = number of protons in the nucleus of an atom. Ex. mass number (A)  = protons + neutrons. Ex. symbol of an atom Ex.   Isotopes  = atoms of the same element with different mass numbers 1
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Ex. See Figure on page 9. atomic weight of X = average weight or mass of all isotopes of a given  element X. Ex.  Note : in the  neutral atom , number of electrons = number of protons cation  = positive ion Ex. anion = negative ion Ex. B. THE PERIODIC TABLE 1. INTRODUCTION - discovered by Mendeleev and Lothar Meyer in 1869 -column = group or family      = elements have similar chemical and physical properties -row = period 2
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2. IMPORTANT ELEMENTS IN OCHEM C, H, O, Si, S, P, Li, Na, Mg, K, and halogens. See Fig. 1.2 Page 10. C. ATOMIC STRUCTURE: THE SHELL MODEL AND  ORBITALS 1. INTRODUCTION -From wave mechanics, electrons in atoms are in energy levels called shells.  In a summary: Shell  subshells orbitals (electron densities) 2. TYPES OF SUBSHELLS a.  s subshells -spherical -one s orbital -can take up to 2 electrons b. p subshells -spherical lobes or dumbbell shape -set of 3 degenerate orbitals (Px, Py, Pz) in a given subshell -can take up to 6 electrons c. d subshells -various shapes -set of 5 d orbitals in a given subshell -can take up to 10 electrons d. f subshells 3
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-various shapes -set of 7 f orbitals in a given subshell -can take up to 14 electrons See Fig. on page 11. Note: Only s and p orbitals are involved in OChem Recall: A node = region with zero electron density. 3. ELECTRON CONFIGURATION EC = Electron distribution in atom Filling order 1s 2s 2p 3s 3p 4s 3d 4p………… → → → → → → → Ex. Do Problem 1.1 and 1.2 page 12  D. THE NATURE OF THE CHEMICAL BOND    1. INTRA AND INTERMOLECULAR FORCES: A REVIEW -Intermolecular forces = ion-dipole, dipole-dipole, H bonds, London  Dispersion Forces (or van der Waals’ Forces): determine physical properties -Intramolecular forces = ionic bonds, covalent bonds, coordinate covalent  bonds, metallic bonds: determine chemical properties Note: covalent bonds are the bonds mostly encountered in organic  compounds. 4
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Recall: metal + nonmetal = ionic compound nonmetal + nonmetal = covalent or molecular compound. 2. VALENCE SHELL ELECTRONS -Outermost shell electrons Ex: Na, Cl, Ne Note: only valence electrons are involved in chemical reactions. 3.
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This note was uploaded on 04/19/2011 for the course CHEMISTRY 2423 taught by Professor Kay during the Spring '08 term at Dallas Colleges.

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Ochem_UNIT_2 - OCHEMUNIT2:STRUCTUREANDBONDING A...

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