Lecture 39 – Lecture 40 Naming Molecules Ozgur Unal NIS – CHEMISTRY Lecture 39 – Lecture 40 Naming Molecules Ozgur Unal

Naming Compounds Many molecular compounds have common names: H2O  water CH3COOH  vinegar All molecular compounds have scientific names: CO2  Carbon dioxide H2SO4  Sulfuric acid We will learn the rules to name binary molecular compounds, binary acids and oxyacids. Binary molecular compounds are composed of only two nonmetal atoms, such as H2S, CO2, N2O. Acids (binary and oxy-) contain covalent bonds, this is why we study them here.

Naming Binary Molecular Compunds Rules for naming binary molecular compounds: 1- The first element in the formula is always named first, using the entire element name. 2- The second element in the formula is named using its root and adding the suffix –ide. 3- Prefixes are used to indicate the number of atoms of each element that are present in the compound  Table 8.3. Example: N2O3  dinitrogen trioxide SCl2  Sulfur dichloride

Naming Binary Molecular Compunds There are exceptions to using the prefixes in step 3: The prefix mono- in the first element in the compound is never used  Carbon dioxide (CO2) If using a prefix results in two consecutive vowels, one of the vowels is usually dropped  Dinitrogen pentoxide (N2O5) Example: Name the following compounds a) P2O5 b) SO2 c) NF3 d) CCl4 a) diphosphorus pentoxide b) sulfur dioxide c) nitrogen trifluoride c) carbon tetrachloride

Naming Binary Molecular Compunds Example: Write the formula for the following compounds diarsenic trioxide dihydrogen monoxide phosphorus pentachloride a) As2O3 b) H2O c) PCl5

Naming Binary Acids Water solutions of some molecules are acidic, and are named as acids. If a compounds produces H+ in solution, it is an acid. Example: HCl A binary acid contains hydrogen and one other element. The rules for naming binary acids: 1- The first word has the prefix hydro- to name the hydrogen part of the compound. The rest of the first word consists of a form of the root of the second element plus the suffix -ic. 2- The second word is always acid. Example: HCl  Hydrochloric acid.

Examples: HI  Hydroiodic acid H2S  Hydrosulfuric acid Naming Binary Acids Examples: HI  Hydroiodic acid H2S  Hydrosulfuric acid If an acid does not contain oxygen, even if it is not a binary acid, these two rules can be used to name them. The root of the second part of the name is the root of the polyatomic ion that the acid contains. Example: HCN is composed of Hydrogen (H) and Cyanide (CN) HCN  Hydrocyanic acid

Naming Oxyacids An acid that contains both a hydrogen atom and an oxyanion is referred to as an oxyacid. Rules for naming an oxyacid: 1- First, identify the oxyanion present. The first word of an oxyacid’s name consists of the root of the oxyanion and the prefix per- or hypo- if it is part of the name, and a suffix. If the oxyanion’s name ends with the suffix –ate, replace it with the suffix –ic. If the name of the oxyanion ends with the suffix –ite, replace it with the suffix –ous. 2- The second word of the name is always acid. Example: HNO3  Nitric acid Example: HNO2  Nitrous acid

Examples: HClO3  ? HClO2  ? H2SO4  ? H2SO3  ? Naming Oxyacids Examples: HClO3  ? HClO2  ? H2SO4  ? H2SO3  ? HClO3  Chloric acid HClO2  Chlorous acid H2SO4  Sulfuric acid H2SO3  Sulfurous acid

Writing Formulas From Names Write the formulas for the following molecules: Silver chloride Dihydrogen monoxide Chlorine trifluoride Diphosphorus trioxide Carbonic acid Hydrochloric acid Dicarbon tetrahydride Hydrobromic acid Sulfurous acid Bromous acid Sulfuric acid AgCl H2O CF3 P2O3 H2CO3 HCl C2H4 HBr H2SO3 HBrO2 H2SO4