CH 6 Chemical Bonding 6.1 Into to chemical bonding Ionic bonding: cations and anions Covalent bonding: share e- Non-polar covalent: share e- equally Polar covalent: uneven sharing of e-

6.2 Covalent Bonding and Molecular Compounds Chemical formula: numbers of atoms of each kind in a chemical compound, uses atomic symbol and subscript Molecular formula: types and numbers of atoms combined in single molecule of molecular compound Covalent Bonds: Attracted and repelled Affected by distance

Bond Length Octet Rule Avg distance between them at minimum PE Bond energy; E required to break bond; kJ/mol Octet Rule Noble gases stable b/c full 8e- in outer shell (s&p) By gaining/losing/sharing e- atoms get full octet Exceptions: H (2e-), B (6e-), BF3, F/O/S (over 8e-)

6.3Ionic Bonding and Ionic Compounds Ionic bonding: cation and anion make neutral compound Formula unit: collection of atoms that an ionic compound can be written Electron-dot can help show bonds of ionic compounds

Crystal Lattice Lattice Energy Ions minimize PE by combining in organized arrangement Lattice Energy E released when 1mol of ionic crystalline compound is formed from gaseous ions Negative is E given off

Polyatomic Ions: charged group of covalently bonded atoms Ionic Properties: Molecular compounds: Forces of attraction not strong lower melting pt; Many even gases at room temp Ionic compounds: strong attractive forces  higher melting/boiling pts; hard but brittle; molten state are electrical conductors Polyatomic Ions: charged group of covalently bonded atoms

6.4 Metallic Bonding Attraction of metal atoms and surrounding e- Highest energy levels occupied by few e- Outer energy levels overlap and allow e- join

Metallic Properties: Bond Strength: Freedom of e-  high electrical/thermal conductivity Strong absorbers/reflectors of light Many orbitals separated by little space allows for absorbing light frequencies; move e- higher E orbital e- drops back/reradiated, so accounts luster Malleable: shaped/ thin sheets Ductility: drawn/pulled into wires Bond Strength: Varies with charge Heat of vaporization: amount of E to break bonds

6.5 Molecular Geometry VSPER Theory: repulsion of sets of valence e- surrounding atom causes them to be as far apart as possible Unshared e- pairs will still affect geometry (b/c negative charge will repel other e-)

Hybrid orbitals Dipoles Equal energies created by combination of 2+ orbitals no same atom Dipoles Equal and opposite charges at a short distance

London- dispersion forces H-bonding H bonds to electronegative atom London- dispersion forces Intermolecular attractions from constant motion of e- creates instantaneous dipoles Only forces acting on noble gases and nonpolar molecules