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Chemical Bonding Part Two: Covalent Bonds and Bond Character v Electronegativity - the relative ability of an to attract in a vThe greater the electronegativity difference, the stronger the bond is that forms between them vIf the electronegativity difference is: • Less than 0.5, then the bond is nonpolar covalent • Between 0.5 and 1.6, the bond is polar covalent • Greater than 1.6, then the bond is ionic Calculating Bond Character Electronegativity Determine the type of bond: Chart 2.55 1. H and O 3.44-2.20 = 1.2 3.04 POLAR COVALENT 0.82 2. Ca and F 3.98-1.00 = 2.98 3.98 IONIC 2.20 3.44 3. Ba and O 3.44-0.89 = 2.55 1.00 IONIC 3.98 4. C and O 3.44-2.55 = 0.89 0.89 POLAR COVALENT 2.96 5. N and N 0-NONPOLAR COVALENT

Covalent Bonds vCharacterized by a sharing of electrons vThe attraction of two for a shared pair of electrons is called a v In a covalent bond, atoms share electrons and neither atom has an ionic charge vA compound whose atoms are held together by covalent bonds is a covalent compound vMolecules are formed from covalent bonds

Single and Multiple Covalent Bonds

v When more than one pair of electrons are shared between atoms multiple covalent bonds form vThese can be double or triple bonds depending on the number of pairs of electrons shared Single and Multiple Covalent Bonds Characteristics of Covalent Bonds v Low melting points

v Do not conduct electricity in any state

v are often soft or brittle

v Many are at room temperature

v Most are less soluble in than ionic compounds and are not electrolytes Polar vs. Nonpolar Covalent Bonds

Nonpolar Covalent Bond v Equal sharing of the bonding pair v Example: In H-H each H atom has an electronegativity value of 2.1 Polar Covalent Bond v Unequal sharing of the bonding v Example: In H-Cl, the electronegativity of the Cl atom is 3.0, while that of the H atom is 2.1 v Electron pair is displaced toward the more electronegative atom v Results in a Formulas for Covalent Bonds 1. Write the symbol of the irst element named -If a preix accompanies the name, place a subscript equal to the preix after the symbol Example: Dinitrogen  N2 2. Write the symbol of the second element - Place a subscript after its symbol if the preix means two or higher

- Example:  N2O3

Formulas for Covalent Bonds Number Preix Number Preix

1 mon(o)- 6 hexa- 2 di- 7 hepta- 3 tri- 8 octa- 4 tetra- 9 nona- 5 penta- 10 deca- Examples:

Carbon dioxide CO2

phosphorous trichloride PCl3

diarsenic pentoxide As2O5

Naming Covalent Compounds 1. Write the name of the irst element 2. If the symbol is followed by a subscript of 2 or more, use the appropriate preix 3. Write the root of the name of the 2nd element with an “–ide” ending 4. Use appropriate preix to denote the number of the 2nd element (1 or more) Examples:

IF5 pentaluoride