Naming Covalent Compounds
• To name a covalent compound, same as ionic naming
except you use prefixes to represent how many atoms of
each element you have
–
–
–
–
–
–
–
–
–
–
1 = mono
2 = di
3 = tri
4 = tetra
5 = penta
6 = hexa
7 = hepta
8 = octa
9 = nona
10 = deca
Naming Molecular Compounds
1. write the name of the element that is the
least electronegative first.
Example: SO2
sulfur
2. Write the name of the second element and
change the ending to “ide”
Example: SO2
sulfur oxide
3. Add a prefix to the beginning of each
element’s name to indicate how many of
atoms of each there are (exception: you do
not write the word mono in front of the first
element if there is only one).
Example: SO2
sulfur dioxide
• If the vowel combination o-o or a-o appear next to
each other in the name, the first of the pair is
omitted
Example: CO
1. Carbon
2. Carbon oxide
3. Carbon monooxide
 carbon monoxide
Practice Problem 1
Name the following molecular compound:
CCl4
Practice Problem 2:
Name the following molecular compound:
N2O4
Exceptions to the naming rule:
• Hydrocarbons/Organic compounds/Alkanes
– Compounds made only of carbon and hydrogen
and single bonds
•
•
•
•
•
•
•
•
•
•
CH4 = methane
C2H6 = ethane
C3H8 = propane
C4H10 = butane
C5H12 = pentane
C6H14 = hexane
C7H16 = heptane
C8H18 = octane
C9H20 = nonane
C10H22 = decane
• If contains double bond
– alkenes
– Change ending to –ene
– ethane ethene
• If contains triple bond
– alkynes
– change ending to –yne
– Propane  propyne
Exceptions to the naming rule:
• Common Names
– H2O = water
– NH3 = ammonia
Writing Molecular Formulas
• Name tells you the elements present and the
number of each atom to write as subscripts.
Example: nitrogen trifluoride
Practice Problem 3:
Write the molecular formula for
tetraphosphorus decoxide.
Practice Problem 4:
Write the molecular formula for dinitrogen
monoxide.