1. Chem 115: Week 3
Dr. Babb
1
Chemical Compounds
Composed of two or more elements which are present in definite proportions
and are chemically bound.
• Chemical Formula: shorthand way of specifying the number and type of
each element in a compound.
• Example: How many atoms of each type are present in the following
compounds?
Ca(OH)2 Mg3(PO4)2 C12H22O11
CaSO4
.5 H2O (CH3)2NH Al2(S2O8)3
Classification of Chemical Compounds: Molecular vs. Ionic
Molecular/Covalent Compounds
• Formed by combination of two or more
nonmetals. Ex. CH4, SiH4, PH3, CO2
• Consist of discrete molecules that
move about as a unit.
• Molecule is the smallest bit of a
molecular compound.
• Chemical formula referred to as
molecular formula.
• Covalent bonds hold together the
atoms in the molecule. Covalent
bonds are due to the sharing of a
pair of e- between atoms.
Ionic Compounds
• Formed by combination of cation
(metal or polyatomic) with an anion
(nonmetal or polyatomic). Ex. KCl,
AlBr3 , Mg3(PO4)2
• Consist of three dimensional array of
ions such that no particular cation
belongs to a particular anion.
• Formula unit is the smallest bit of an
ionic compound.
• Chemical formula referred to as the
formula unit.
• Ionic bonds hold the ions together.
Ionic bonds are due to the
electrostatic forces of attraction
between cations and anions.
2. Chem 115: Week 3
Dr. Babb
2
Classify each of the following compounds as ionic or molecular:
Al2O3 C6H6 XeF4 CaBr2 Na3P
Mg(NO3)2 C8H18 CoSO4 CS2 TiCl4
N2 O2 (NH4)2SO3
Molecules of
the molecular
compound H2O.
3-D array of ions in the
ionic compound NaCl.
Na Na+ + 1 e-
11p 11p
11e- 10e-
Cl + 1 e- Cl-
17p 17p
17e- 18e-
Ions: Polyatomic and Monatomic
• Polyatomic Ions: ions consisting of two or more elements
– atoms are held together by covalent bonds
– ion charge shared over all atoms in ion
– atoms stay together as a unit
Ex. NO3
-, NO2
-, CO3
-2, PO4
-3, SO4
-2, SO3
-2, C2H3O2
-, HCO3
-, etc.
• Monatomic Ions: ions consisting of one atom Ex. Cl-, Al+3, Zn+2, N-3
Charges on monatomic ions can be predicted from position on periodic table.
Metals Nonmetals
IA IIA B-Groups IIIA IVA VA VIA VIIA VIIIA
+1 +2 Variable +3 -4 -3 -2 -1 0
(Fe+2/Fe+3)
Post-transition metals (metals in Groups IIIA –VIA) also have variable charges.
Example: Sn+2/Sn+4, Sb+3/Sb+5
• Example: What ions are present in the following compounds?
K3P AlBr3 Ca3N2 CrBr3 Fe2O3
FeO Mn3(PO4)2 TiSO4 Mn(OH)2 CO2
3. Chem 115: Week 3
Dr. Babb
3
Formula Unit
Chemical formula for an ionic compound. Subscripts specify the
smallest whole number ratio of cation to anion to give a neutral
compound.
• Examples: Give formula units for ionic compounds formed by
combination of the elements or ions below.
sodium and fluorine lithium and oxygen aluminum and carbon
calcium and sulfur potassium and carbonate ammonium and sulfate
iron(III) and acetate strontium and phosphate
Nomenclature
“The naming of chemical compounds.”
Organic Compounds: hydrocarbons (molecules containing H and C) and their
derivatives. Ex. CH4, C8H18, CH3OH, C2H5OH, CH3OCH3
Inorganic Compounds: all other compounds. Ex. NaCl, PBr3, XeF4, CS2, FeO
Naming of Inorganic Compounds
A. Classify the compound: Is the compound ionic, molecular, or an acid?
Note: H usually written first in the chemical formula of an acid.
1. Naming of ionic compounds.
a. Metal cation with NONVARIABLE charge.
i. Name the metal (or cation) first.
ii. Name the nonmetal (or anion) second.
iii. Change ending of nonmetal to –ide.
NOTE: Don’t change ending of polyatomics!!
4. Chem 115: Week 3
Dr. Babb
4
Examples: Provide names for the following ionic compounds.
CaO K2S Mg3P2 SrH2 (NH4)3PO4
Na2SO4 AlBr3 LiNO3 BaCO3
b. Metal cation with VARIABLE charge (transition or post-
transition metal).
STOCK SYSTEM:
i. Name the metal (or cation) first.
ii. Specify charge on metal using Roman numeral
inside parentheses.
iii. Name nonmetal and change ending to –ide.
OR OLD SYSTEM:
i. Name the metal first using the Latin name.
ii. Specify charge on metal by changing ending….
-ous metal cation of lower charge
-ic metal cation of higher charge
iii. Name nonmetal and change ending to –ide.
Examples: Provide names for the following ionic compounds using both the
STOCK and old system.
(Latin names for some metals: ferrum, cuprum, stannum, plumbum,
aurum, stibium)
STOCK old
CrO
Cr2O3
SnCl2
SnCl4
Fe(NO2)2
Fe(C2H3O2)3
5. Chem 115: Week 3
Dr. Babb
5
2. Naming of molecular/covalent compounds.
a. Name the element that comes first in chemical formula
first. (Usually this element lies farthest to left in period. table.)
b. Name the second element and change ending to –ide.
c. Specify number of atoms of each element present by
addition of a Greek number prefix.
Number Greek Prefix Number Greek Prefix
1 mono- 6 hexa-
2 di- 7 hepta-
3 tri- 8 octa-
4 tetra- 9 nona-
5 penta- 10 deca-
Examples: Provide names for the following molecular compounds.
Cl2O7 PCl3 SF6 CO CO2
N2O5 N2O Cl2O XeF4
H2S HCl HBr HI
3. Naming of acids with (aq) designation.
(H usually written first in chemical formula of acid.)
a. Decide whether acid is a BINARY or OXYACID.
Binary Acid – contains H and one other element.
Ex. HCl(aq), HF(aq), H2S(aq)
Oxyacid – contains H, O, and one other element.
Ex. HClO4, H2SO3, HNO2
b. Naming of binary acids.
i. Use root of nonmetal name.
ii. Add hydro- prefix and –ic suffix to root.
Examples: Provide names for the following binary acids.
HCl(aq) HF(aq) HBr(aq) H2Se(aq)
6. Chem 115: Week 3
Dr. Babb
6
c. Naming of oxyacids.
i. Use root of nonmetal name followed by word
acid.
ii. If only two different oxyacids can be formed
from nonmetal, specify which is present by
adding following suffixes.
-ous oxyacid with least oxygens
-ic oxyacid with most oxygens
iii. If four different oxyacids can be formed from
nonmetal, specify which is present by adding
following prefixes and suffixes.
hypo- -ous oxyacid with least oxygens
-ous
-ic
per- -ic oxyacid with most oxygens
Examples: Provide names for the following oxyacids.
HNO2 and HNO3 H2SO4 and H2SO3 HClO2, HClO4, HClO3, and HClO
HBrO3 HIO
4. Naming of polyatomic ions.
Most polyatomic ions are anions derived from oxyacids by removal of
one or more protons (H+).
a. -ous ending of oxyacid is changed to –ite when H+
removed.
-2 H+
Ex. H2SO3 SO3
-2
sulfurous acid sufite anion
b. -ic ending of oxyacid is changed to –ate when H+
removed.
-H+
Ex. HClO4 ClO4
-
perchloric acid perchlorate anion
