Introduction to Chemical Principles Chapter 8: Chemical Nomenclature Gilbert Lewis

Nomenclature Chemical Nomenclature is the system of names used to distinguish compounds from each other and the rules needed to device these names. We will consider how to name: Binary ionic compounds, which contain a metal and a nonmetal. Binary molecular compounds, which consist only of nonmetals. (For naming purposes metalloids are treated as nonmetals) Binary and oxo-acids, compounds that release hydrogen ions when dissolved in water.

Classifying Elements & Compounds Compounds resulting from the combination of a metal and one or nore nonmetal are called ionic Compounds resulting from the combination of a nonmetal with other nonmetal are considered molecule. A binary compound is a compound in which only two element are present A binary ionic compound is an ionic compound in which one element present is a metal and the other element present is a non metal. The metal is always present as the positive ion, and the nonmetal is always present as the negative ion.

For nomenclature purposes, there are two types of metal ions: Fixed Charge metal ions only form one type of positive ion – always has the same charge. Variable Charge metal ions can form more than one type of positive ion, with the ion type differing in charge and magnitude.

Fixed-Charge Metal ions Fixed-charge metals can form only one type of ion.

Variable-Charge Metal Ions Which metals have a variable charge? The rest of them!

Variable-Charge Metal Ions

Naming Binary Ionic Compounds for Metals with Fixed Charge 1. name metal cation first, name nonmetal anion second 2. cation name is the metal name 3. nonmetal anion named by changing the ending on the nonmetal name to -ide

Example: Naming Binary Ionic with Fixed Charge Metal CsF 1. Identify cation and anion Cs = Cs+ because it is Group 1A F = F− because it is Group 7A 2. Name the cation Cs+ = cesium 3. Name the anion F− = fluoride 4. Write the cation name first, then the anion name cesium fluoride

Name the Compound: CaF2 Step 1 From the formula it is a binary compound; only two elements.

Naming Binary Ionic Compounds for Metals with Variable Charge 1. name metal cation first, name nonmetal anion second 2. metal cation name is the metal name followed by a Roman numeral in parentheses to indicate its charge determine charge from anion charge common ions 3. nonmetal anion named by changing the ending on the nonmetal name to -ide

Practice — Find the charge on the cation 1. TiCl4 2. CrO3 3. Fe3N2 4 Cl = 4−,  Ti = 4+ 3 O = 6−,  Cr = 6+ 2 N = 6−,  3 Fe = 6+, Fe = 2+

Example: Naming binary ionic with variable charge metal CuF2 1. Identify cation and anion F = F− because it is Group 7 Cu = Cu2+ to balance the two (−) charges from 2 F− 2. Name the cation Cu2+ = copper(II) 3. Name the anion F− = fluoride 4. Write the cation name first, then the anion name copper(II) fluoride Tro: Chemistry: A Molecular Approach, 2/e

Example: Writing formula for binary ionic compounds containing variable charge metal manganese(IV) sulfide 1. Write the symbol for the cation and its charge 2. Write the symbol for the anion and its charge 3. Charge (without sign) becomes subscript for other ion 4. Reduce subscripts to smallest whole number ratio 5. Check that the total charge of the cations cancels the total charge of the anions Mn4+ S2- Mn4+ S2− Mn2S4 MnS2 Mn = (1)∙(4+) = +4 S = (2)∙(2−) = −4

Practice — What are the formulas for compounds made from the following ions? copper(II) ion with a nitride ion iron(III) ion with a bromide ion Cu3N2 Cu2+ with N3− Fe3+ with Br− FeBr3

Name the following compounds 1. TiCl4 2. PbBr2 3. Fe2S3 titanium(IV) chloride lead(II) bromide iron(III) sulfide

Some Common Polyatomic Ions

Patterns for Polyatomic Ions 1. Elements in the same column form similar polyatomic ions same number of O’s and same charge ClO3− = chlorate \ BrO3− = bromate 2. If the polyatomic ion starts with H, add hydrogen- prefix before name and add 1 to the charge CO32− = carbonate \ HCO3− = hydrogen carbonate

Periodic Pattern of Polyatomic Ions -ate groups

Example: Naming ionic compounds containing a polyatomic ion Na2SO4 1. Identify the ions Na = Na+ because in Group 1A SO4 = SO42− a polyatomic ion 2. Name the cation Na+ = sodium, metal with invariant charge 3. Name the anion SO42− = sulfate 4. Write the name of the cation followed by the name of the anion sodium sulfate

Writing Names of Binary Molecular Compounds of Two Nonmetals 1. Write name of first element in formula a) element furthest left and down on the Periodic Table b) use the full name of the element 2. Writes name the second element in the formula with an -ide suffix a) as if it were an anion, however, remember these compounds do not contain ions! 3. Use a prefix in front of each name to indicate the number of atoms a) Never use the prefix mono- on the first element

Subscript – Prefixes 1 = mono- 2 = di- 3 = tri- 4 = tetra- 5 = penta- not used on first nonmetal 2 = di- 3 = tri- 4 = tetra- 5 = penta- 6 = hexa- 7 = hepta- 8 = octa- 9 = nona- 10 = deca- Drop last “a” if name begins with a vowel

Example: Naming binary molecular BF3 1. Name the first element boron 2. Name the second element with an –ide fluorine  fluoride 3. Add a prefix to each name to indicate the subscript monoboron, trifluoride 4. Write the first element with prefix, then the second element with prefix a) drop prefix mono from first element boron trifluoride

Name the Following NO2 PCl5 I2F7 nitrogen dioxide phosphorus pentachloride diiodine heptafluoride Tro: Chemistry: A Molecular Approach, 2/e

Example: Binary Molecular dinitrogen pentoxide Identify the symbols of the elements nitrogen = N oxide = oxygen = O Write the formula using prefix number for subscript di = 2, penta = 5 N2O5 Tro: Chemistry: A Molecular Approach, 2/e

Write Formulas for the Following dinitrogen tetroxide sulfur hexafluoride diarsenic trisulfide N2O4 SF6 As2S3

Common Ions Shown on the Periodic Table

An acid is a H-containing molecular compound whose molecules yield hydrogen ions (H+) when dissolved in H2O. Acids produce H+ in H2O, but an anion is also produced, depending on the structure of the molecular compound. E.g., HCl  H+ + Cl- HNO3  H+ + NO3- HCN  H+ + CN-

Acids If the anion does not contain oxygen, the acid is named with the prefix hydro– and the suffix –ic. Examples: HCl Hydrochloric acid HCN Hydrocyanic acid H2S Hydrosulfuric acid

Acids If the anion does contain oxygen: The suffix –ic is added to the root name if the anion name ends in –ate. Examples: HNO3 Nitric acid H2SO4 Sulfuric acid HC2H3O2 Acetic acid

Acids If the anion does contain oxygen: The suffix –ous is added to the root name if the anion name ends in –ite. Examples: HNO2 Nitrous acid H2SO3 Sulfurous acid HClO2 Chlorous acid

Flowchart for Naming Acids

Acid Nomenclature

The oxy-ions of chlorine, bromine and iodine all have these trends in common. Look for them below…… perchlorate ClO4-1 chlorate ClO3-1 chlorite ClO2-1 hypochlorite ClO-1 Perbromate BrO4-1 Bromate BrO3-1 Bromite BrO2-1 Hypobromite BrO-1 Periodate IO4-1 Iodate IO3-1 Iodite IO2-1 Hypoiodite IO-1 The most productive method of committing these ions to memory is first memorize the ones that have the “ate” ending. This is the most common ending.

Common Student Missteps For ionic compounds, formulas must be reduced to simplest ratios. Ex: MnO2, not Mn2O4 (Don’t reduce molecular compounds.) There is a difference between ammonia (NH3) and ammonium ion (NH4+). Chemical formulas do not show ionic charges. Ex: NaCl, not Na+Cl- Don’t put parentheses unless they are needed to show more than one of the same ion. Ex: NaNO3, not Na(NO3)

Choose the correct formula for the compound Practice Problem #2 hydrobromic acid Choose the correct formula for the compound 1. HBrO(aq) 2. HBr(aq) 3. HBrO3(aq) 4. HBrO2(aq) 5. none of the above