Vocabulary

   Dipole - represented by an arrow; The arrow points toward the negative charge center, and the cross tail indicates the positive center of the charge. Intramolecular forces - The bonding forces that hold the atoms of a molecule together. Intermolecular forces - The forces that occur amoung molecules that cause them to aggregate to form a solid or a liquid. Molar heat of fusion - The energy required to melt 1 mole of a substance. Molar heat of vaporization- The energy required to change 1 mole of liquid to its vapor. Bond Energy- The energy required to break a given chemical bond Covalent Bond- A type of bond in which atoms share electrons Polar Covalent Bond- A covalent bond in which the electrons are not shared equally because one attracts them more strongly than the other Ionic Bond- The attraction between oppositely charged ions Electronegativity- The tendency of an atom in a molecule to attract shared electrons to itself  Duet Rule - A term describing the distribution of valence electrons when hydrogen atoms - which end up with only two valence electrons - experience chemical bon A term describing the distribution of valence electrons when hydrogen atoms—which end up with only two valence electrons—experience chemical bonding with other atoms. Most other elements follow the octet rule. Octet Rule - The observation that atoms of nonmetals form the most stable molecules when their valence shell has 8 electrons Lone Pairs - An electron pair that is localized on a given atom; an electron pair not involved in bonding Valence Electrons - The electrons in the outermost occupied principal quantum level of an atom Resonance Structure - Various lewis structures ** Dipole-dipole attraction: Dipole-dipole forces are attractive forces between the positive end of one polar molecule and the negative end of another polar molecule. ** ** Hydrogen bonding: Describes an important form of partial valiancy bonding; occurs between one covalently bounded hydrogen atom to an electronegative element and the lone electron pair of an another electronegative atom; water and liquid acetic acid are typical examples. ** <span style="FONT-FAMILY: Arial, Helvetica, sans-serif">** London Dispersion forces: The London dispersion force is the weakest intermolecular force. The London dispersion force is a temporary attractive force that results when the electrons in two adjacent atoms occupy positions that make the atoms form temporary dipoles. This force is sometimes called an induced dipole-induced dipole attraction. London forces are the attractive forces that cause nonpolar substances to condense to liquids and to freeze into solids when the temperature is lowered sufficiently. ** <span style="FONT-FAMILY: Arial,Helvetica,sans-serif"><span style="FONT-FAMILY: Arial, Helvetica, sans-serif">** Anisotropic: Materials that are anisotropic have non-uniform spatial distribution of optical properties (for example, refraction, transmission, reflection). In polarized light and DIC microscopy, anisotropy refers to the preferential orientation of optical properties with respect to the vibration plane of linearly polarized light. **  <span style="FONT-FAMILY: Arial,Helvetica,sans-serif">
 * Vocabulary **
 * Van der Waals forces: **** Van der Waals forces include attractions between atoms, molecules, and surfaces. They differ from covalent and ionic bonding in that they are caused by correlations in the fluctuating polarizations of nearby particles (a consequence of quantum dynamics). **