Section 8.2 Naming Molecules Translate molecular formulas into binary molecular compound names. oxyanion: a polyatomic ion in which an element (usually a nonmetal) is bonded to one or more oxygen atoms Name acidic solutions. oxyacid Specific rules are used when naming binary molecular compounds, binary acids, and oxyacids.

Why do atoms bond? (cont.) Gaining or losing electrons makes atoms more stable by forming ions with noble-gas electron configurations. (octet) Sharing valence electrons with other atoms also results in noble-gas electron configurations. The chemical bond that results from sharing electrons is a covalent bond. A molecule is formed when two or more nonmetal atoms bond.

Shared electrons are considered to be part of the outer energy level of all the atoms that share it. This type of bonding usually occurs between elements near each other on the periodic table. Most of this type of bonding is done with nonmentals.

Molecular Nomenclature (Naming) Prefix System (binary compounds) Less electronegative atom comes first. The first element is always named first using the entire element name. Add prefixes to indicate the subscripts of each atom. Omit the mono- prefix on first element. Change the ending of the second element to -ide.

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

Name the following: P2O5 Name the two elements: Phosphorus and Oxygen For the second element, the name is changed to oxide. Add the prefixes to show the number of atoms. Diphosphorus pentoxide

Exception to the prefixes in table 8.3: The first element never uses the mono prefix If using a prefix would cause two consecutive vowels, one of the them is often dropped to avoid a difficult pronunciation. CO is monoxide NOT monooxide.

Molecular Nomenclature CCl4 N2O SF6 carbon tetrachloride dinitrogen monoxide sulfur hexafluoride

Molecular Nomenclature arsenic trichloride dinitrogen pentoxide tetraphosphorus decoxide AsCl3 N2O5 P4O10

Molecular Nomenclature The Seven Diatomic Elements, exist naturally as 2 atom molecules H2 N2 O2 F2 Cl2 Br2 I2 H N O F Cl Br I

Naming Binary Molecular Compounds (cont.) Many compounds were discovered and given common names long before the present naming system was developed. (water H2O, ammonia NH3, hydrazine N2H4, and nitric oxide NO are examples). These compounds are generally known by their common names instead of their scientific ones. What would their scientific names be?

Naming Acids Acids Examples: Compounds that form [H+] in Solution (water). Formulas begin with ‘H’. Examples: HCl – hydrochloric acid HNO3 – nitric acid H2SO3 – sulfurous acid

Anion Ending Acid Name Acid Nomenclature -ide -ate -ite Hydro-(stem)-ic acid (stem)-ic acid (stem)-ous acid

Acid Nomenclature HBr H2CO3 H2SO3  hydrobromic acid  carbonic acid Br ends in -ide  hydrobromic acid CO3 ends in -ate  carbonic acid SO3 ends in -ite  sulfurous acid

Acid Nomenclature hydrofluoric acid sulfuric acid nitrous acid  H+ F- Fluoride  H+ F-  HF Sulfate  H+ SO42-  H2SO4 Nitrite  H+ NO2-  HNO2

Notice that hydrogen is not part of the name. Naming Acids (cont.) The second word is always acid. Notice that hydrogen is not part of the name.

Naming Acids (cont.) An acid, whether a binary acid or an oxyacid, can have a common name in addition to its compound name.

A B C D Section 8.2 Assessment Give the name for the molecule HClO4. A. perchloric acid B. chloric acid C. chlorous acid D. hydrochloric acid A B C D Section 8-2