L2-Naming Molecules.pdf

Lesson 2 Naming Molecules  Focus Question How do you name molecules?  New Vocabulary oxyacid  Review Vocabulary oxyanion: a polyatomic ion in which an element (usually a nonmetal) is bonded to one or more oxygen atoms  Naming Binary Molecular Compounds...

Lesson 2 Naming Molecules  Focus Question How do you name molecules?  New Vocabulary oxyacid  Review Vocabulary oxyanion: a polyatomic ion in which an element (usually a nonmetal) is bonded to one or more oxygen atoms  Naming Binary Molecular Compounds Example: N2O The first element is always named first using the entire element name. N is the symbol for nitrogen. The second element is named using its root and the suffix –ide. O is the symbol for oxygen so the second word is oxide.  Naming Binary Molecular Compounds Example: N2O (continued) Prefixes are used to indicate the number of atoms of each element that are present in the compound. The table on the next slide lists the most common prefixes used. There are two atoms of nitrogen and one atom of oxygen so the first word is dinitrogen and the second word is monoxide. Naming Binary Molecular Compounds NAMING BINARY MOLECULAR COMPOUNDS Use with Example Problem 2. SOLVE FOR THE UNKNOWN Problem The first element, represented by P, is Name the compound P2O5, which is used as phosphorus. a drying and dehydrating agent. Phosphorus The second element, represented by O, is Response oxygen. Add the suffix –ide to the root of ANALYZE THE PROBLEM oxygen, ox-. You are given the formula for a compound. The Oxide formula contains the elements and the Combine the names. number of atoms of each element in one Phosphorus oxide molecule of the compound. Because only two different elements are present and both are Now modify the names to indicate the number nonmetals, the compound can be named using of atoms present in a molecule. the rules for naming binary molecular compounds. Naming Binary Molecular Compounds EVALUATE THE ANSWER SOLVE FOR THE UNKNOWN The name diphosphorus pentoxide shows From the formula P2O5, you know that two that a molecule of the compound contains phosphorus atoms and five oxygen atoms two phosphorus atoms and five oxygen make up a molecule of the compound. atoms, which agrees with the compound’s From Table 3, you know that di- is the chemical formula, P2O5. prefix for two and penta- is the prefix for five. The a in penta- is not used because oxide begins with a vowel. diphosphorus pentoxide  Naming Binary Molecular Compounds Common Names for Some Molecular Compounds Many compounds were discovered and given common names long before the present naming system was developed. Examples: Water Ammonia Hydrazine Nitric oxide  Naming Acids Naming Binary Acids A binary acid contains hydrogen and one other element. Example: HCl The first word has the prefix hydro- to name the hydrogen part of the compound. The rest of the word consists of a form of the root of the second element plus the suffix –ic. HCl (hydrogen and chlorine) becomes hydrochloric. The second word is always acid. Thus, HCl in a water solution is called hydrochloric acid.  Naming Acids Naming Oxyacids An oxyacid contains both a hydrogen atom and an oxyanion. Example: HNO3 The first word 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 ends with –ate, replace it with –ic. If it ends with –ite, replace it with –ous. NO3– the nitrate ion, becomes nitric. The second word is always acid. HNO3 (hydrogen and nitrogen ion) becomes nitric acid.  Quiz 1. Which is name of the acid HNO2? A nitrate B nitric acid C nitrous acid CORRECT D nitrate acid  Quiz 2. Which is the molecular compound name for water? A hydrogen dioxide C dihydrogen monoxide CORRECT B hydrogen monoxide D dihydrogen dioxide  Quiz 3. What is the name for H2SO3? A hydrosulfide C sulfurous acid CORRECT B hydrosulfite D sulfuric acid  Quiz 4. Which describes a binary molecular compound? A composed of two metal atoms B composed of a metal atom and a nonmetal atom C composed of two nonmetal atoms CORRECT D composed of two metal atoms  Quiz 5. What type of acid contains hydrogen and one other element? A oxyacid C oxyanion B molecular covalent acid D binary acid CORRECT