VIEWS: 9 PAGES: 13 POSTED ON: 2/15/2012
3.2 How Atoms Combine Compounds • Two or more elements • Ex: combined chemically. water carbon dioxide table salt Chemical Bonds • Covalent bonds • Ionic bonds • Metallic bonds Covalent Bonds • Electrons are shared. • Both elements nonmetals. • Molecules are formed with covalent bonds. • Ex: H2O CO2 C6H12O6 Ionic Bonds • Electrons are transferred. • One atom gains, one loses electrons. • Electrical attraction between ions of opposite charge. • Between metal – nonmetal. • Ex: NaCl, KF, CaBr2 Ionic Bond Metallic Bonds • In metals, valence electrons are shared, free to move about. • Metal—metal. • Metals conduct electricity easily. Polar Covalent Molecules • Electrons are shared, but not equally. • Some atoms have a stronger pull for the electrons. • Molecule not symmetrical in shape (unbalanced). Nonpolar Covalent Molecules • Equal distribution of charge around a central atom. • Molecule has a symmetrical shape Water Molecule • Water is a polar molecule. • Electrons are not shared equally by the H and O atoms. Surface tension • Water molecules stick together. • Forms a thin surface on top.
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