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CHAPTER 7
Chemical Formulas and
Chemical Compounds
Section 7-1: Chemical Names and Formulas
Monatomic ions—ions formed from a single atom
Binary compounds—compounds composed of two different elements
Nomenclature—naming system (i.e., binomial nomenclature, Life Science)
Oxyanions—polyatomic ions that contain oxygen
Salt—an ionic compound composed of a cation and the anion from an acid
d-Block elements
1+
copper(I)
Cu+
silver
Ag+
2+
cadmium
chromium(II)
cobalt(II)
copper(II)
iron(II)
lead(II)
manganese(II)
mercury(II)
nickel(II)
tin(II)
vanadium(II)
zinc
Table 7-3 Numerical Prefixes
1
2
3
4
monoditritetra-
Cd2+
Cr2+
Co2+
Cu2+
Fe2+
Pb2+
Mn2+
Hg2+
Ni2+
Sn2+
V2+
Zn2+
5
penta-
3+
chromium(III)
iron(III)
lead(III)
vanadium(III)
6
hexa-
Cr3+
Fe3+
Pb3+
V3+
7
hepta-
4+
lead(IV)
Pb4+
vanadium(IV) V4+
tin(IV)
Sn4+
8
octa-
9
nona-
10
deca-
Section 7-2: Chemical Names and Formulas
Oxidation numbers or states—assigned to the atoms composing the compound
or ion in order to show the general distribution of electrons
Assigning Oxidation Numbers
1. The atoms in a pure element, i.e., Na, O2, and P4, have an oxidation number of zero.
2. The more-electronegative element in a binary molecular compound is assigned the
number equal to the negative charge it would have as an anion. The less-
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electronegative atom is assigned the number equal to the positive charge it would
have as a cation.
3. Fluorine, as the most electronegative element, always has an oxidation number of –1.
4. Oxygen is almost always a –2. Exceptions are peroxides, such as H2O2, where its
oxidation number is –1, and halogens, such as OF2, where its oxidation number is +2.
5. Hydrogen has an oxidation number of +1 in all compounds containing elements that
are more-electronegative than it, and a –1 in compounds with metals.
6. The sum of oxidation numbers of the atoms in a neutral compound is equal to zero.
7. The sum of the oxidation numbers of all atoms in a polyatomic ion is equal to the
charge of the ion.
Rules 1 through 7 apply to covalently bonded atoms, but can also be assigned to atoms in
ionic compounds.
Section 7-3: Using Chemical Formulas
Formula mass—sum of the average atomic masses of all the atoms represented
in a formula
Percentage composition—(mass of element in sample of compound / mass of
sample of compound) * 100 = % element in compound
Section 7-4: Determining Chemical Formulas
Empirical formula—consists of the symbols for the elements combined in a
compound, with subscripts showing the smallest whole-number mole ratio of the
different atoms in the compound
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