Chem1201PReviewCh8

Chem1201PReviewCh8 - Chemistry 1201 Review/Preview Chapter...

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Chemistry 1201 Review/Preview Chapter Eight Review Guide Dr. Saundra McGuire Spring 2007 Basic Concepts of Chemical Bonding I. Chemical Bonds, Lewis Symbols, and the Octet Rule A. Chemical Bond – the strong attraction between two atoms or ions 1. Ionic Bond – the electrostatic attraction between ions of opposite charges 2. Covalent Bond – The bond formed due to sharing of electrons between atoms 3. Metallic bond – The bond found in metals, due to freely moving electrons in the metal. B. Lewis Symbols – show the symbol of an atom, along with the valence electrons. (See Table 8.1 for the Lewis symbols of many of the elements.) C. The Octet Rule states that atoms will gain, lose, or share electrons in order to obtain eight electrons in their valence shell. II. Ionic Bonding A. Energetics of Ionic Bond Formation When forming ionic bonds from neutral atoms, and electrons must be removed from the neutral metal atoms to form cations; electrons must be added to the nonmetal atom to form anions; and the cations and anions must be in close enough proximity for the electrostatic attraction to be felt. Therefore, formation of an ionic bond involves different energies: ionization energy, electron affinity, and lattice energy. The ionization energy is positive (forming the cation requires energy input), the electron affinity is generally negative (forming the anion generally releases energy), and the formation of the lattice releases energy. (See pages 305 – 306 and lecture notes for a more complete discussion.) B. Electron Configuration of Ions of the Representative Elements The atoms of elements in groups 1A, 2A, and 3A form cations with charges of +1, +2, and +3, respectively. The atoms of elements in groups 5A, 6A, and 7A form anions with charges of -3, -2, and -1, respectively. C. The Transition Metals The transition metals lose their s electrons first, and then d electrons. Therefore the charges on transition metal ions are generally +1, +2, or +3, depending on how many s and d electrons are lost. III. Lewis Structures A. What are they? Lewis structures show the arrangement of electrons in a molecule. The electrons shown are the valence electrons of all of the atoms in the molecule.
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Chem1201PReviewCh8 - Chemistry 1201 Review/Preview Chapter...

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