Molecular Compounds and Acids Chapter 9 Sections 3-4

Binary Molecular Compounds Binary ionic compounds are composed of a metal and a non-metal (cation and anion) Binary ionic compounds are composed of a metal and a non-metal (cation and anion) Binary molecular compounds are composed of two nonmetallic elements. Binary molecular compounds are composed of two nonmetallic elements. This affects the way we name and write formulas for these compounds This affects the way we name and write formulas for these compounds

When two nonmetallic elements combine, they can do so in more than one way When two nonmetallic elements combine, they can do so in more than one way Ex. CO, CO 2, CO 3 2-, C 2 O 4 2- Ex. CO, CO 2, CO 3 2-, C 2 O 4 2- Each of the above have very different properties Each of the above have very different properties We can’t call all of them carbon oxide… We can’t call all of them carbon oxide… We need to name them in a way that distinguishes between the different compounds We need to name them in a way that distinguishes between the different compounds

Naming Binary Molecular Compounds We need to use prefixes to help distinguish between different compounds. We need to use prefixes to help distinguish between different compounds. See p 269 Table 9.4 See p 269 Table 9.4 The number in the table refers to how many atoms of each element are in the compound The number in the table refers to how many atoms of each element are in the compound

CO CO Carbon monoxide Carbon monoxide Mono indicates 1 oxygen atom Mono indicates 1 oxygen atom CO 2 CO 2 Carbon dioxide Carbon dioxide Di indicates 2 oxygen atoms Di indicates 2 oxygen atoms When naming binary molecular compounds: When naming binary molecular compounds: The second element in the name ends with “ide” (same as binary ionic compounds) The second element in the name ends with “ide” (same as binary ionic compounds) The vowel of the prefix is often dropped The vowel of the prefix is often dropped Ex. Carbon monoxide instead of carbon monooxide Ex. Carbon monoxide instead of carbon monooxide If the first element in the name has just one atom, drop the mono- prefix for that element. If the first element in the name has just one atom, drop the mono- prefix for that element. Ex. Carbon monoxide instead of monocarbon monoxide Ex. Carbon monoxide instead of monocarbon monoxide

Name the following: N 2 O N 2 O Dinitrogen monoxide Dinitrogen monoxide PCl 3 PCl 3 Phosphorous trichloride Phosphorous trichloride SF 6 SF 6 Sulfur Hexafluoride Sulfur Hexafluoride

Writing Formulas for Binary Molecular Compounds Use the name to write the formula Use the name to write the formula Use the prefixes to tell you the subscript Use the prefixes to tell you the subscript Ex. Tetraiodine nonoxide Ex. Tetraiodine nonoxide I 4 O 9 I 4 O 9 Sulfur Trioxide Sulfur Trioxide SO 3 SO 3 Phosphorous Pentafluoride Phosphorous Pentafluoride PF 5 PF 5

Write the formulas for the following: Nitrogen Triflouride Nitrogen Triflouride NF 3 NF 3 Disulfur Dichloride Disulfur Dichloride S 2 Cl 2 S 2 Cl 2 Dinitrogen Tetroxide Dinitrogen Tetroxide N 2 O 4 N 2 O 4

Acids Simple definition (to become more complicated later…) Simple definition (to become more complicated later…) Acid: a compound that produces hydrogen ions (H + ) when dissolved in water Acid: a compound that produces hydrogen ions (H + ) when dissolved in water Think of them as ions connected to as many hydrogen ions as are needed to make the molecule electrically neutral Think of them as ions connected to as many hydrogen ions as are needed to make the molecule electrically neutral

Naming Acids 2 types: 2 types: Binary Acids: Acids containing only hydrogen and a nonmetal Binary Acids: Acids containing only hydrogen and a nonmetal Oxoacids: Acids containing hydrogen, a nonmetal, and oxygen Oxoacids: Acids containing hydrogen, a nonmetal, and oxygen

Naming Binary Acids Hydro + base name of nonmetal + ic Acid Hydro + base name of nonmetal + ic Acid Ex. HCl Ex. HCl Hydrochloric Acid Hydrochloric Acid HBr HBr Hydrobromic Acid Hydrobromic Acid

Naming Oxoacids Oxoacids include polyatomic ions Oxoacids include polyatomic ions Ex. HNO 3 comes from H + and NO 3 - Ex. HNO 3 comes from H + and NO 3 - Nitric Acid Nitric Acid If the oxyanion ends with –ate If the oxyanion ends with –ate Base name of oxyanion + ic Acid Base name of oxyanion + ic Acid Ex. H 2 SO 4 is sulfuric acid Ex. H 2 SO 4 is sulfuric acid If the oxyanion ends with –ite If the oxyanion ends with –ite Base name of oxyanion + ous acid Base name of oxyanion + ous acid H 2 SO 3 is sulfurous acid H 2 SO 3 is sulfurous acid

Name the following Acids HI HI Hydroiodic acid Hydroiodic acid HC 2 H 3 O 2 HC 2 H 3 O 2 Acetic Acid Acetic Acid H 2 S H 2 S Hydrosulfuric Acid Hydrosulfuric Acid

Relationship Acid suffixoxoanion Acid suffixoxoanion -ic-ate anion -ic-ate anion -ous-ite anion -ous-ite anion I got SICK from something I ATE. I got SICK from something I ATE. This is a little memory-helper to remember which acid suffix goes with each oxoanion! This is a little memory-helper to remember which acid suffix goes with each oxoanion!

Application: Acid Rain Acid rain occurs when rainwater mixes with air pollutants such as NO, NO 2, and SO 2, that form acids. NO and NO 2, primarily from vehicular emissions, combine with water to form HNO 3. SO 2, primarily from coal-powered electricity generation, combines with water to form H 2 SO 4. HNO 3 and H 2 SO 4 both cause rainwater to become acidic. The problem is the greatest in the northeastern US where pollutants from Midwestern electrical power plants combine with rainwater to produce rain with acid levels that are up to ten times as high as normal. Acid rain occurs when rainwater mixes with air pollutants such as NO, NO 2, and SO 2, that form acids. NO and NO 2, primarily from vehicular emissions, combine with water to form HNO 3. SO 2, primarily from coal-powered electricity generation, combines with water to form H 2 SO 4. HNO 3 and H 2 SO 4 both cause rainwater to become acidic. The problem is the greatest in the northeastern US where pollutants from Midwestern electrical power plants combine with rainwater to produce rain with acid levels that are up to ten times as high as normal.