# Classifying Binary Compounds

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Classifying Binary Compounds
Binary ionic compounds contain a metal and a nonmetal. Type I and II Compounds containing two nonmetals Type III Compounds containing H and a nonmetal = Acids 4

Metal Cations Type I Type II
Metals that can only have one possible charge Charge determined by position on the Periodic Table (group 1A: +1; group 2A: +2) Type II Metals that can have more than one possible charge (transition metals) Metal cation’s charge (usually +1, +2, +3, or +4) determined from the charge on anion 6

The Modern Periodic Table

Type I Binary Ionic Compounds
Contain Metal Cation from Groups 1A, 2A or Al, Ga, & In (metals with only one possible ionic charge) + Nonmetal Anion Metal listed first in formula & name Name metal cation first, name nonmetal anion second Nonmetal anion named by changing the ending on the nonmetal name to –ide 7

Name the following Type I Compounds:
You must know the simple cations and anions in Table 5.1 MgCl2 K2O CaBr2 BaS

Type II Binary Ionic Compounds
Metal cation name is the metal name followed by a Roman numeral in parentheses to indicate its charge Determine charge from anion charge Common Type II cations in Table 5.2 Nonmetal anion named by changing the ending on the nonmetal name to -ide

Determining the Charge on a Cation – Au2S3
Determine the charge on the anion Au2S3: the anion is S, since it is in Group 6A, and its charge is –2 Determine the total negative charge Since there are 3 S in the formula, the total negative charge is –6 Determine the total positive charge Since the total negative charge is -6, the total positive charge is +6 Divide by the number of cations Since there are 2 Au in the formula & the total positive charge is +6, each Au has a +3 charge 9

Name the following Type II compounds:
CrCl3 CrCl2 Cu2O CuO Fe2S3

Type III - Binary Compounds of Two Nonmetals
Name first element in formula first. Use the full name of the element. Name the second element in the formula as if it were an anion. However, remember these compounds do not contain ions! Use a prefix in front of each name to indicate the number of atoms. Never use the prefix mono- on the first element. 10

mono- (not used on first nonmetal)
Prefixes octa- 8 hepta- 7 hexa- 6 penta- 5 tetra- 4 tri- 3 di- 2 mono- (not used on first nonmetal) 1 Prefix Subscript Drop last “a” in the prefix if the name begins with vowel: N2O5 dinitrogen pentoxide (not pentaoxide) 11

Name the following Type III compounds:
CCl4 N2O3 PCl3 PCl5 CO

Classify and name the following binary compounds:
OCl2 CaBr2 CuS B2O3

Compounds Containing Polyatomic Ions
Polyatomic ions are charged entities that contain more than one atom (e.g. HSO4-) Must memorize name, formula, and charge Table 5.4 Polyatomic compounds contain one or more polyatomic ions. To name these compounds you must learn to recognize the polyatomic ions. (NH4C2H3O2) ammonium acetate 12

Compounds Containing Polyatomic Ions (cont.)
Name polyatomic compounds by naming cation and anion. Non-polyatomic ions named like Type I and II Na2SO4 sodium sulfate Polyatomic acids contain H+ and a polyatomic anion.

Names of Common Polyatomic Ions

Oxyanions -ate ion -ate ion plus 1 O  same charge, per- prefix
chlorate = ClO3- -ate ion plus 1 O  same charge, per- prefix perchlorate = ClO4- -ate ion minus 1 O  same charge, -ite suffix chlorite = ClO2- -ate ion minus 2 O  same charge, hypo- prefix, -ite suffix hypochlorite = ClO- 14

Patterns for Polyatomic Ions
Elements in the same column on the periodic table form similar polyatomic ions. Same number of O’s and same charge ClO3- = chlorate  BrO3- = bromate If the polyatomic ion starts with H, add hydrogen- before the ion’s name and add one to the charge. CO32- = carbonate  HCO3- = hydrogen carbonate 13

Name the following compounds:
Na3PO4 FeCO3 (NH4)2CO3 Ca(CN)2

Naming Acids Formulas always begin with H as first element
Can be thought of as consisting of H+ cation and anion Binary acids have H+ cation and a nonmetal anion Oxyacids have H+ cation and a polyatomic anion 15

Naming Acids (cont) If the anion does not contain oxygen, use the prefix hydro- plus the suffix –ic attached to the root name of the element followed by the word acid. HBr: When the anion contains oxygen, use the root name of the central element of the anion, with a suffix –ic or –ous, followed by the word acid. When the anion name ends in -ate, the suffix –ic is used. When it ends in –ite, the suffix –ous is used. H2SO4: H2SO3: HNO3: HNO2:

Naming Acids (Summary)

Writing Formulas from Names
For Type I, Type II, polyatomic compounds and acids: Determine the ions present. Determine the charges on the cation and anion. Balance the charges to get the subscripts. For Type III compounds, use the prefixes to determine the subscripts. 16

Write the formula for each of the following compounds:
diboron trioxide copper(III) bromide chromium (II) permanganate phosphorus tribromide