Chemical Bonding Covalent Bonding

A. Types of Bonds IONIC COVALENT Bond Formation e- are transferred from metal to nonmetal e- are shared between two nonmetals Type of Structure crystal lattice true molecules Physical State solid liquid or gas Melting Point high low Solubility in Water yes usually not Electrical Conductivity yes (solution or liquid) no Other Properties odorous

A. Types of Bonds METALLIC e- are delocalized among metal atoms Bond Formation e- are delocalized among metal atoms Type of Structure “electron sea” Physical State solid Melting Point very high Solubility in Water no yes (any form) Electrical Conductivity Other Properties malleable, ductile, lustrous

Covalent Bonding - True Molecules A. Types of Bonds Covalent Bonding - True Molecules Diatomic Molecule RETURN

B. Bond Polarity Most bonds are a blend of ionic and covalent characteristics. Difference in electronegativity determines bond type.

B. Bond Polarity Electronegativity Attraction an atom has for a shared pair of electrons. higher e-neg atom  - lower e-neg atom +

B. Bond Polarity Electronegativity Trend Increases up and to the right.

B. Bond Polarity Nonpolar Covalent Bond e- are shared equally symmetrical e- density usually identical atoms Electronegativity difference range 0.00 – 0.4

+ - B. Bond Polarity Polar Covalent Bond e- are shared unequally asymmetrical e- density results in partial charges (dipole) Electronegativity difference range 0.4 – 2.0 + -

B. Bond Polarity - + Nonpolar Covalent - no charges Polar Covalent - partial charges + -

B. Bond Polarity Nonpolar Polar Ionic View Bonding Animations.

B. Bond Polarity Examples: Cl2 HCl 3.0-3.0=0.0 Nonpolar 3.0-2.1=0.9 NaCl 3.0-3.0=0.0 Nonpolar 3.0-2.1=0.9 Polar 3.0-0.9=2.1 Ionic

Determining Type, DEN 0.3 1.7 5% 50%

Determining Type, DEN Ionic, Polar or Nonpolar Covalent Compounds: The difference in electronegativity between bonding atoms leads to the type of compound. Example: O2 , O=O ENO = 3.5 D EN = 0 g NO , N=O ENN = 3.0, ENO = 3.5 D EN = .5 g CO , C= O ENC = 2.5, ENO = 3.5 D EN = 1.0 g NaCl , Na+Cl- ENNa = 0.9, ENCl = 3.0 D EN = 2.1 g Nonpolar Covalent Polar Covalent Polar Covalent Ionic

Sample Problem Use electronegativity differences to classify bonding between sulfur, S, and the following elements: hydrogen, H; cesium, Cs; and chlorine, Cl. In each pair, which atom will be more negative? Bonding between sulfur and Electronegativity difference More-negative atom Bond type hydrogen 2.5 – 2.1 = 0.4 Polar-covalent sulfur cesium 2.5 – 0.7 = 1.8 Ionic sulfur chlorine 3.0 – 2.5 = 0.5 Polar-covalent chlorine

Additional Sample Problems Complete the following chart: Elements bonded Electronegativity difference More-negative atom Bond type a. C and H 2.5 – 2.1 = 0.4 Polar-covalent carbon b. C and S 2.5 – 2.5 = 0 Nonpolar covalent Same electronegativity c. O and H 3.5 – 2.1 = 1.4 Polar-covalent oxygen d. Na and Cl 3.0 – 0.9 = 2.1 Ionic chlorine e. Cs and S 2.5 – 0.7 = 1.8 Ionic sulfur

LecturePLUS Timberlake Learning Check Identify the type of bond between the following atoms A. K-N 1) nonpolar 2) polar 3) ionic B. N-O 1) nonpolar 2) polar 3) ionic C. Cl-Cl 1) nonpolar 2) polar 3) ionic LecturePLUS Timberlake

LecturePLUS Timberlake Solution A. K-N 3) ionic B. N-O 2) polar C. Cl-Cl 1) nonpolar LecturePLUS Timberlake

Covalent Bonds can have multiple bonds, so you should be familiar with the following… Single Covalent Bond- chemical bond resulting from sharing of an electron pair between two atoms. Double Covalent Bond- chemical bond resulting from sharing of two electron pairs between two atoms. Triple Covalent Bond -chemical bond resulting from sharing of three electron pairs between two atoms.

C. Molecular Nomenclature Prefix System (binary compounds) 1. Less e-neg atom comes first. 2. Add prefixes to indicate # of atoms. Omit mono- prefix on first element. 3. Change the ending of the second element to -ide.

C. Molecular Nomenclature PREFIX mono- di- tri- tetra- penta- hexa- hepta- octa- nona- deca- NUMBER 1 2 3 4 5 6 7 8 9 10

C. Molecular Nomenclature CCl4 N2O SF6 carbon tetrachloride dinitrogen monoxide sulfur hexafluoride

C. Molecular Nomenclature arsenic trichloride dinitrogen pentoxide tetraphosphorus decoxide AsCl3 N2O5 P4O10