Chapter 7 – Chemical
Formulas and
Chemical Compounds
7-1 Chemical Names and
Formulas

What’s so important about a chemical
formula?
It indicates the relative # of atoms of
each kind in a chemical compound
 Molecular Compound: chemical
formula reveals the # of atoms in a
single molecule. C8H18
 Ionic Compound: consists of a lattice
of positive and negative ions held
together by mutual attraction. 
Simplest ratio NaCl

Al2(SO4)3- How many atoms
are there?
Al
2
S
3
O
12
Monoatomic Ions
Ions formed from a single atom
 Ex. Na  Na1+ , O  O2 Not all main-group elements form
ions, C and Si form covalent bonds
instead of ionic bonds
 Sn and Pb are exceptions  lose only
2 e-s instead of 4 or sometimes they
keep all 4 electrons.

Naming Monoatomic Ions
Cations are identified by the elements
name
 Anions the ending of the element’s
name is dropped.

The ending –ide is added.
 Ex. Fluorine (F) = Fluoride ion (F-)
 Nitrogen (N) = Nitride (N3-)
 Flash Cards may be useful to
memorize these!!!!

Binary Ionic Compounds
Compounds composed of two
different elements.
 Ex. Magnesium and Bromine form
Magnesium Bromide, MgBr2

Rules for Ionic Compounds

1. Write the symbols for the ions side by
side. The cations go first.

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2. Cross over the charges by using the
absolute value of each ion’s charge as the
subscript for the other ion.
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Al 3+ O 2-
Al2O3
3. Check subscript and divide them by their
largest common factor to give the smallest
possible whole-number ration.
4. Write the formula
Write the formula for the
following:
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Magnesium and iodine
Potassium and sulfur
Aluminum and chlorine
Zinc and bromine
Cesium and sulfur
Strontium and oxygen
Calcium and nitrogen
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MgI2
K2S
AlCl3
ZnBr2
Cs2S
SrO
Ca3N2
Name the following:
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BaF2
CaO
AgF
CdO
K3N
NaI
AlBr3
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Barium Fluoride
Calcium Oxide
Silver Fluoride
Cadmium Oxide
Potassium Nitride
Sodium Iodide
Aluminum Bromide
The Stock System of
Nomenclature
Some elements form two or more ions
such as Fe, with different charges.
 This system uses Roman numerals to
indicate an ions’ charge
 Fe 2+ or Fe 3+
 FeCl2 = iron (II) chloride
 FeCl3 = iron (III) chloride

Write the formula and give
the name for the following:
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Cu + and O 2Fe 3+ and S 2Cu 2+ and Cl Sn 2+ and Cl Hg 2+ and O 2Sn4+ and S 2V 2+ and F V 4+ and Br -
Name the following:
CoI2
 HgI2
 PbS2
 CuBr2

Compounds Containing
Polyatomic ions
Oxyanions- polyatomic ions
containing oxygen
 Nitrate vs. Nitrite – (-ite less oxygen)


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NO3- and NO2-
Sulfates, Nitrate, Chlorates
Write the formulas for:
Copper(II) nitrate
 Potassium iodide
 Sodium hydroxide
 Ammonium acetate
 Calcium carbonate
 Potassium permanganate
 Sodium sulfate
 Iron(III) nitrate

Name the following:
Ag2S
 NaMnO4
 Ba(OH)2
 NH4NO3
 Fe(ClO)2
 Ca(NO3)2
 K2SO3
 NaCH3COO

Naming Binary Molecular
Compounds
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#
1
2
3
4
5
6
7
8
9
10
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#
Mono
Di
Tri
Tetra
Penta
Hexa
Hepta
Octa
Nona
deca
Rules for Molecular
Compounds
1. The least electronegative element
is first. It is given a prefix if it is more
than one
 2. the second element is named by
combining a prefix, the root of the
word, and –ide ending
 3. the o or a at the end of the prfix is
usually dropped when the word
following begins with another vowel.

Examples.
As2O5 = diarsenic pentoxide
 PF5 = phosphorus pentafluoride
 XeF4 = Xenon tetrafluoride
 CCl4 = carbon tetrachloride
 Carbon dioxide = CO2
 Dinitrogen pentoxide = N2O5
 Sulfur hexafluoride = SF6
 Dinitrogen monoxide = N2O

Acids and Salts
Acids can be binary acids or oxyacids
 Binary acids are acids that consist of
H and a halogen, HCl hydrochloric
acid
 Oxyacids, contain H, P and a third
element, Sulfuric Acid, H2S
 Pg 214
