Chapter 9
Chemical Names and Formulas
Mr. Roberts
Chemistry Level 2
Section 1 – Naming Cations
Group A Elements
• Just write name of metal and add “ion” to
ending
• Example:
– Na+1
– Al+3
sodium ion
aluminum ion
Naming Cations
Group B Elements (transition metals)
• Ionic charge will change so write Roman
Numerals in parenthesis after name of metal
to indicate charge. (Stock System)
– Table 9.2 page 255
Naming Cations
• Some post transition element also have charges
that will change.
– Ex: Tin and Lead
• Sn+2
• Pb+2
Sn+4
Pb+4
• Some transition metals only have one ionic
charge. Therefore you don’t use roman numerals.
– Silver
– Cadmium
– Zinc
Ag+1
Cd+2
Zn+2
Naming Anions
• Always have the same charge!
– Change suffix with - ide
– Ex:
F-1
Fluoride ion
O-2 Oxide ion
Polyatomic Ions
• Group of atoms that stay together and have
an overall charge
• Usually end with –ate or –ite (one less oxygen)
• Ex:
(SO3)-2
Sulfite
(SO4)-2
Sulfate
(NH4)+1
ammonium
Section 2 – Writing/Naming Ionic
Compounds
Finding the formulas for ionic compounds.
• Criss-Cross Method
• Remember…ionic compounds must be
expressed in the lowest whole number ratio.
Naming Ionic Compounds
• Binary Ionic Compounds (2 ions)
– Use rules for naming ions
– Ex:
Na+1Cl-1 {sodium ion and chloride ion}
NaCl
Sodium Chloride
Naming Ionic Compounds (continued)
• Naming Ternary Ionic Compounds (involving a
polyatomic ion group)
• Name it as it appears
• Ex:
CaCO3
calcium carbonate
Mg3(PO4)2
magnesium phosphate
CaSO4
calcium sulfate
• If ammonium or any other polyatomic cation is
reacting with a monatomic anion use binary ionic
rules
Naming Group B Ionic Compounds
• Rules for naming binary and ternary ionic
compounds apply
• Include a roman numeral in parenthesis to
indicate the ionic charge.
– Use the reverse of the criss cross method to
determine the charge.
– Ex:
Section 3 – Molecular Compounds
Naming Binary molecular compounds (2
nonmetals)
• Name the elements in order they appear.
• Drop ending of second element and replace with
suffix “ide”.
• Use prefixes to indicate # of atoms present
– Table 9.4 page 269
Binary Molecular Compounds
Mono = 1
Di = 2
Tri = 3
Tetra = 4
Penta = 5
Hexa = 6
Hepta = 7
Octa = 8
Nona = 9
Deca = 10
Examples:
N2O
CO2
CO
SF6
dinitrogen monoxide
carbon dioxide
carbon monoxide
sulfur hexafluoride
9.4 Naming and Writing Acids
• Acid: a compound contain H+ ions.
Anion
Ending
Acid Name
with Suffix
Acid
Ending
Example
- ide
hydro________ic
acid
HCl – hydrochloric
acid
- ite
____________ous
acid
H2SO3 – sulfurous
acid
- ate
_____________ic
acid
H2SO4 – sulfuric
acid
Examples
HF
Hydrofluoric Acid
HClO2
Chlorous Acid
HClO3
Chloric Acid
Naming and Writing Bases
• Base: a compound containing OH-1
• Named in the same way as other ionic
compounds
• Example: NaOH sodium hydroxide
Section 9.5 – The Laws Governing
Formulas and Names
We are able to name compounds and write their
formulas because they form from elements in
predictable ways
1. The Law of Definite Proportions
• In samples of any chemical compound, the
masses of the elements are always in the
same proportions.
2. The Law of Multiple Proportions
• Whenever the same two elements form more
than one compound, the different masses of
one element that combine with the same
mass of the other element are in the ratio of
small whole numbers.
– John Dalton