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Chapter 8. Covalent Bonding I. Molecules and Molecular Cpds. noble gases (e.g. He and Ne) and most elements are monatomic. Molecules and Molecular Cpds. Covalent cpds atoms held together by sharing e- are joined by a covalent bond to form covalent cpds. Non-metals
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Chapter 8 Covalent Bonding I
Molecules and Molecular Cpds noble gases (e.g. He and Ne) and most elements are monatomic.
Molecules and Molecular Cpds Covalent cpds • atoms held together by sharing e- are joined by a covalent bond to form covalent cpds • Non-metals • e.g. [O2 ;not a cpd], CO2, C6H12O6 element
Molecules and Molecular Cpds Covalent bonds • not so strong as Ionic bonds (electrostatic attractions). • Covalent cpds: made up of ALLnonmetals (how about ionic cpds?)
Molecules and Molecular Cpds Molecule • a neutral group of atoms (all nonmetals) joined together by covalent bonds. • may be a cpd (e.g. CO2) or an element (e.g. N2) covalent cpds = molecular cpds
Molecules and Molecular Cpds • e.g. air contains oxygen molecules (O2) and nitrogen molecules (N2)---not cpds Adiatomic elementconsists of 2 atoms. e.g. 7 diatomic elements are H2, N2, O2, F2, Cl2, Br2, I2
A Hydrogen Molecule • 2 H atoms share a pair of e- in a covalent bond. A covalent bond is formed by 2 shared e-.
Covalent Bonds • 2 of the same atoms form a covalent bond, e.g., when 2 F atoms form the F2 molecule. • a pair of valence e- are shared---single covalent bond (2 shared e-). • Form octets of for both atoms Shared pair of e-
Molecules and Molecular Cpds Molecular cpd (covalent cpd): - cpds composed of molecules • e.g. H2O , CO2 , C6H12O6
Covalent Bonds • All diatomic elements (F2, Cl2, Br2, I2, O2, N2, and H2) have covalent bonds. • are molecules (not molecular cpds) • The other molecules are ALLcpds • Most of the elemental diatomic molecules are gases at room temp—Cl2, F2, O2, N2, and H2.
Modeling Water • 2 covalent bonds. • octet • duplet
Lone (unshared) pair 3 covalent bonds Bonding (shared) pair
A Model for Ammonia Lone pair • Each H shares a pair of e- with the N. • N’s remaining 2 e- form a lone pair. • N has a complete octet of e-.
Modeling Carbon Dioxide • double bond • sharing 2 pairs of e- between 2 atoms.
9.3 Naming Binary Molecular Cpds (1) Name the elements in the order listed in the formula. (2) Use prefixes to indicate the # of each kind of atom.
9.3 Naming Binary Molecular Cpds (3) Omit the prefix mono- when the formula contains only 1 atom of the 1st element in the name. e.g. CO2 (we don’t say monocarbon) (4) The suffix of the name of the 2nd element is -ide.
9.3 Writing Formulas for Binary Mol. Cpds (5) Use the prefixes in the name to tell the subscript of each element in the formula. (6) Then write the correct symbols for the 2 elements with the appropriate subscripts.
9.3 Naming BinaryMolecular Cpds
CST problem 1 (picture of a circuit) The above picture shows a light bulb connected to a battery with the circuit interrupted by a solution. When dissolved in the water to form a 1.0 molar solution, all of the following substances will complete a circuit allowing the bulb to light except A hydrochloric acid B sodium nitrate C sucrose D ammonium sulfate
CST problem 2 What type of bond do all of the molecules in the table above have in common? A covalent B ionic C metallic D polar