CHEMICAL NAMES
& FORMULAS
To describe the atomic
makeup of compounds,
chemists use systematic
methods for naming
compounds and writing
formulas.
Chemical Formulas

Subscript directly behind an atom
applies to that atom only.
H2O

Subscripts outside of parentheses
applies to all atoms inside the
parentheses.
Al2(SO4)3
Monatomic Ions



Ions formed from a single atom.
Written as element symbol w/charge
as superscript.
Monatomic cations (+)
• simply element’s name.

Monatomic anions (-)
• ending of element’s name is dropped.
• ending –ide is added.
Examples of Monatomic Ions

Write formulas for the following
monatomic ions:
Lithium
Bromide

Nitride
Iron (II)
Write names for the following
monatomic ions:
Ba2+
Cl-
Sn4+
Mg2+
S2Cu2+
Binary Ionic Compounds

Composed of 2 different elements.
Total (+) and (-) charges must be
equal.
• Magnesium Flouride



Mg2++ F- = MgF2
Must have 2 (-) F’s to equal (+) 2 charge of
Mg.
Charges Crossover.
To name combine names of cation
and anion with cation being first.
• ZnS
Zinc Sulfide
Binary Ionic Compound
Examples

Write the formula for the binary ionic compounds
formed between the following elements:
Zinc & Iodine
Sodium & Oxygen

Zinc & Sulfur
Calcium & Nitrogen
Name the binary ionic compounds indicated by
the following formulas:
AgCl
BaO
SrF2
CaBr2
ZnO
CaCl2
Stock System of
Nomenclature

System used to distinguish between
cations of elements that form more
than one cation. Uses Roman
Numerals.
• CuCl2
Copper (II) Chloride
Examples of Stock System
of Nomenclature

Write the formula and give the name
of the compounds formed between
the ions:
Cu2+ & BrFe3+ & O2-

Give the names for the following
compounds:
CuO
SnI4
CoF3
FeS
Polyatomic Ions
Most Common
 1 Less O
 2 Less O’s
 1 More O

-ate
-ite
hypoper-
Compounds Containing
Polyatomic Ions



Same as Binary Ionic
Compounds
Name of Cation given 1st, Name
of Anion 2nd.
When Writing formula, put
parentheses around anion if
more than one is present in the
compound.
Examples of Compounds
Containing Polyatomic Ions

Write the formula for the following:
Tin (IV) Sulfate
Sodium Iodide

Calcium Nitrite
Copper (II) Sulfate
Give the name for the following
compounds:
Ag2O
KClO3
KClO
Ca(OH)2
NH4OH
FeCrO4
Naming Binary
Molecular Compounds


Unlike ionic compounds, molecular
compounds are composed of individual
covalently bonded units.
Scientists use 2 systems to name these
compounds, the 1st uses prefixes.
Rules for the Prefix System
1.
2.
The less-electronegative element is
given 1st. It is given a prefix only if
it contributes more than 1
molecule.
2nd element is named by:
 Prefix indicating # of atoms
 Root of the element
 The ending –ide
3.
When a prefix is used and the root
begins w/a vowel, the o or a of the
prefix is dropped.
General Electronegativity Order
C, P, N, H, S, I, Br, Cl, O, F
Mono is normally omitted on 2nd
element.
Binary Molecular Compound
Examples

Name the following Binary Molecular
Compounds:
SO3

ICl3
PBr5
Write formulas for the following
compounds:
• Carbon Tetraiodide
• Phosphorus Trichloride
• Dinitrogen Trioxide
Oxidation Numbers



Used in New System – Stock System
Same as Stock System used for
Binary Ionic Compounds.
Roman Numeral is used for Oxidation
Number of 1st element in a
compound. 2nd element is named
with name ending in –ide.
Assignment
Page 236
(#’s: 27, 28, & 29)
Using
Chemical
Formulas
Formula Mass
Sum of all the average
atomic masses of all the
atoms represented in a
formula unit.
 Round to 2 decimal places.

Calculating Formula Mass
Average Atomic Mass H:
1.01 amu
Average Atomic Mass O:
16.00 amu
2H atoms X 1.10amu/H atom =
2.02 amu
1O atom X 16.00amu/O atom =
16.00 amu
Average Atomic Mass H2O:
2.02 amu + 16.00 amu =
18.02 amu H2O
Find the Formula Mass for
each of the following:
Potassium Chlorate
Sulfuric Acid
Calcium Nitrate
Phosphate Ion
Magnesium Chloride
Assignment
Page 236
(# 30)
Molar Mass