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7: Bonding and Intermolecular Forces

  • Page ID
    329778
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    How do atoms make compounds? Typically they join together in such a way that they lose their identities as elements and adopt a new identity as a compound. These joins are called chemical bonds. But how do atoms join together? Ultimately, it all comes down to electrons. Before we discuss how electrons interact, we need to introduce a tool to simply illustrate electrons in an atom.

    • 7.1: Representing Valence Electrons with Dots
      The Lewis Structure of a molecule shows how the valence electrons are arranged among the atoms of the molecule. Lewis electron dot diagrams use dots to represent valence electrons around an atomic symbol. Lewis electron dot diagrams for ions have less (for cations) or more (for anions) dots than the corresponding atom. From experiment, chemists have learned that when a stable compound forms, the atoms usually have a noble gas electron configuration or eight valence electrons.
    • 7.2: Lewis Structures of Ionic Compounds- Electrons Transferred
      The tendency to form species that have eight electrons in the valence shell is called the octet rule. The attraction of oppositely charged ions caused by electron transfer is called an ionic bond. The strength of ionic bonding depends on the magnitude of the charges and the sizes of the ions.
    • 7.3: Covalent Lewis Structures- Electrons Shared
      Covalent bonds are formed when atoms share electrons. Lewis electron dot diagrams can be drawn to illustrate covalent bond formation. Double bonds or triple bonds between atoms may be necessary to properly illustrate the bonding in some molecules.
    • 7.4: Writing Lewis Structures for Covalent Compounds
      Lewis dot symbols provide a simple rationalization of why elements form compounds with the observed stoichiometries. A plot of the overall energy of a covalent bond as a function of internuclear distance is identical to a plot of an ionic pair because both result from attractive and repulsive forces between charged entities. In Lewis electron structures, we encounter bonding pairs, which are shared by two atoms, and lone pairs, which are not shared between atoms.
    • 7.5: Resonance - Equivalent Lewis Structures for the Same Molecule
      Resonance structures are averages of different Lewis structure possibilities. Bond lengths are intermediate between covalent bonds and covalent double bonds.
    • 7.6: Predicting the Shapes of Molecules
      The approximate shape of a molecule can be predicted from the number of electron groups and the number of surrounding atoms.
    • 7.7: Electronegativity and Polarity- Why Oil and Water Don’t Mix
      Covalent bonds can be nonpolar or polar, depending on the electronegativities of the atoms involved. Covalent bonds can be broken if energy is added to a molecule. The formation of covalent bonds is accompanied by energy given off. Covalent bond energies can be used to estimate the enthalpy changes of chemical reactions.
    • 7.8: Interactions between Molecules
      All substances experience dispersion forces between their particles. Substances that are polar experience dipole-dipole interactions. Substances with covalent bonds between an H atom and N, O, or F atoms experience hydrogen bonding. The preferred phase of a substance depends on the strength of the intermolecular force and the energy of the particles.
    • 7.9: Evaporation and Condensation
      Evaporation is the conversion of a liquid to its vapor below the boiling temperature of the liquid. Condensation is the change of state from a gas to a liquid. As the temperature increases, the rate of evaporation increases.
    • 7.10: Melting, Freezing, and Sublimation
      Phase changes can occur between any two phases of matter. All phase changes occur with a simultaneous change in energy. All phase changes are isothermal.
    • 7.11: Intermolecular Forces- Dispersion, Dipole–Dipole, Hydrogen Bonding, and Ion-Dipole
      All substances experience dispersion forces between their particles. Substances that are polar experience dipole-dipole interactions. Substances with covalent bonds between an H atom and N, O, or F atoms experience hydrogen bonding. The preferred phase of a substance depends on the strength of the intermolecular force and the energy of the particles.


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