Chemical Bonding

Chemical compounds

Chemical bond: attractive force holding two or more atoms together. Ionic bond results from the transfer of electrons from a metal to a nonmetal. Covalent bond results from sharing electrons between the atoms. Usually found between nonmetals. Metallic bond attractive force holding pure metals together. Chemical Bonds, Lewis Symbols, and the Octet Rule

Ionic Compounds

Ionic Bonds: One Big Greedy Thief Dog!

Covalent Bonding

Polar Covalent Bonds: Unevenly matched, but willing to share.

Metallic Bonding

Metallic Bonds: Mellow dogs with plenty of bones to go around.

Covalent Bonding

Lewis Symbols Chemical Bonds, Lewis Symbols, and the Octet Rule

Drawing Lewis Structures Follow Step by Step Method 1.Total all valence electrons. [Consider Charge] 2.Write symbols for the atoms and guess skeleton structure [ define a central atom ]. 3.Place a pair of electrons in each bond. 4.Complete octets of surrounding atoms. [ H = 2 only ] 5.Place leftover electrons in pairs on the central atom. 6.If there are not enough electrons to give the central atom an octet, look for multiple bonds by transferring electrons until each atom has eight electrons around it.

Exceptions to the Octet Rule Central Atoms Having Less than an Octet Relatively rare. Molecules with less than an octet are typical for compounds of Groups 1A, 2A, and 3A. Most typical example is BF 3, with only 6 Formal charges indicate that the Lewis structure with an incomplete octet is more important than the ones with double bonds.

There are five fundamental geometries for molecular shape: Molecular Shapes: VSEPR

Figure 9.3 HyperChem

e-pairsNotationName of VSEPR shapeExamples 2AX 2 LinearHgCl 2, ZnI 2, CS 2, CO 2 3AX 3 Trigonal planarBF 3, GaI 3 AX 2 ENon-linear (Bent)SO 2, SnCl 2 4AX 4 TetrahedralCCl 4, CH 4, BF 4 - AX 3 E(Trigonal) PyramidalNH 3, OH 3 - AX 2 E 2 Non-Linear (Bent)H 2 O, SeCl 2 5AX 5 Trigonal bipyramidalPCl 5, PF 5 AX 4 EDistorted tetrahedral (see-sawed) TeCl 4, SF 4 AX 3 E 2 T-ShapedClF 3, BrF 3 AX 2 E 3 LinearI 3 -, ICl 2 - 6AX 6 OctahedralSF 6, PF 6 - AX 5 ESquare PyramidalIF 5, BrF 5 AX 4 E 2 Square PlanarICl 4 -, BrF 4 -

Timberlake LecturePLUS27

Timberlake LecturePLUS28

Molecular Geometries and Bonding Polarity

S O O Just as electrons push away from each other, so do molecules HBr HBr is a polar molecule: dipole-dipole forces. There are also dispersion forces between HBr molecules. CH 4 CH 4 is nonpolar: London dispersion forces, caused by “temporary dipoles”. SO 2 SO 2 is a polar molecule: dipole-dipole forces. There are also dispersion forces between SO 2 molecules.

S O O What type(s) of intermolecular forces exist between each of the following molecules? HBr HBr is a polar molecule: dipole-dipole forces. There are also dispersion forces between HBr molecules. CH 4 CH 4 is nonpolar: dispersion forces. SO 2 SO 2 is a polar molecule: dipole-dipole forces. There are also dispersion forces between SO 2 molecules. Intermolecular Forces

Hydrogen Bond The hydrogen bond is a special dipole-dipole interaction between they hydrogen atom in a polar N-H, O-H, or F-H bond and an electronegative O, N, or F atom. A H … B A H … A or A & B are N, O, or F

Intermolecular Forces Dispersion Forces Attractive forces that arise as a result of temporary dipoles induced in atoms or molecules ion-induced dipole interaction dipole-induced dipole interaction