Naming Chemical
Compounds
Review
What is a chemical formula?
• shorthand representation of the
composition of a substance using
atomic symbols and numerical
subscripts
• can represent a molecule (covalent
bonded structure) or a formula unit
(ionic bonded structure)
Review
Significance of a chemical
formula
• formula tells number and type of
atoms in a molecule or formula unit
(one atom difference can cause
change in properties)
• Examples: Ag, NaCl, HCl, Al2(SO4)3,
CaSO4  5 H2O, etc.
Naming Ionic Compounds
Binary ionic compounds
• Metal named first
• Name of non-metal has –ide added
• If metal has more than one possible
charge use stock system (Roman
numerals) or common name
Ex: NaCl, KI, FeF2, FeF3
Naming Ionic Compounds
Compounds with polyatomic
ions
• Cation is named first (using stock or common
name)
• Anion is named second (using name of
polyatomic ion)
Al2(CO3)3, BaSO4, CaSO3, Fe(NO3)2, NH4Cl
(DO NOT change endings of polyatomic ions!!!)
Naming Ionic Compounds
Hydrates
• ionic compounds that absorb
water into their structures
• named like regular ionic
compounds, add numeric prefix
and hydrate at the end
Naming Ionic Compounds
Prefixes:
1: mono2: di3: tri4: tetra5: penta-
6: hexa7: hepta8: octa9: nona10: deca-
Naming Ionic Compounds
Hydrates
•
•
ionic compounds that absorb water into their structures
named like regular ionic compounds, add numeric prefix and hydrate at the end
MgSO4  7 H2O, CuSO4  5 H2O
Naming Molecular
Compounds
Binary molecular compounds
• Element from left-most part of
table is named first
• Name of second element has
–ide added
• Use Greek prefixes to indicate
number of atoms
Naming Molecular
Compounds
Prefixes:
1: *mono-
6: hexa(*only with second element)7: hepta2: di8: octa3: tri9: nona4: tetra10: deca5: penta-
Naming Molecular
Compounds
Binary molecular compounds
•
•
•
Element from left-most part of table is named first
Name of second element has –ide added
Use Greek prefixes to indicate number of atoms
CO, CCl4, N2O, N2O3
Naming Molecular
Compounds
Acids
• when in water, produce H+ ions, name usually from
characteristic anion
• Hydro acids: hydro + name of halogen + -ic + acid
HCl, HF, HBr
• Oxoacids: polyatomic ion + acid (use –ous and –ic as
needed, -ic goes with > # O atoms)
H2SO4, HNO2, HNO3
Naming Chemical
Compounds
Given: Chemical Formula
Wanted: Name of Compound
• Need to ask questions to determine which
naming rules to use
• Here is one set of questions you could use…
Has a metal?
Yes
No
Yes
No
No
Yes
Yes
No
Yes
No
Writing Formulas
• Use the criss-cross method –
the charges (superscripts) go
to the bottom (as subscripts)
and switch from right to left
Writing Formulas
Examples:
•
•
•
•
•
Fe3+ + Cl1- becomes
Al3+ + O2- becomes
Sn2+ + O2- becomes
Mg2+ + (OH)1- becomes
NH41+ + SO42- becomes
•
•
•
•
•
FeCl3
Al2O3
SnO
Mg(OH)2
(NH4)2SO4
Writing Formulas
• Remember: you are looking for
the smallest whole-number
ratio of ions that will give an
overall charge of 0 – that’s
why the 3rd example has no
subscripts (2+ +2- = 0)