Naming Covalent
(Molecular)
Compounds
Properties of Covalently
Bonded Compounds
• Usually TWO NONMETALS bonded together
• Two nonmetals share electrons between them
• Can be Gases, Liquids or “squishy” solids.
• Generally have LOW melting and boiling points
• Do not conduct electricity well
• Usually not very soluble in water
How are covalent compounds
different than Ionic ones?
Ionic
Covalent
• Metal – Nonmetal bond
• Nonmetal-Nonmetal bond
• Electrons are transferred
• Electrons are shared
• Generally solid
• Solid, Liquid or gas
• High Melting/Boiling pts
• Low Melting/Boiling pts
• Conduct electricity when
melted or dissolved
• Do not conduct
What is the basic structural unit of
a covalent compound?
• Covalent compounds form MOLECULES
• Bonding between atoms in a molecule is
generally much, much stronger than the
attraction between different molecules.
• Married couples analogy…
How are covalent compounds
different than Ionic ones?
Ionic
• Basic Structural unit is the
“Unit cell” or the
“formula unit”
• Ions arranged in crystal
structure
Covalent
• Basic structural unit is the
MOLECULE
• Molecules may attract each
other but that attraction is
small compared with
internal bonding
Naming
molecules from
their formulas
Use the Prefixes…
1 – mono
2 – Di
3 – Tri
4 – Tetr(a)
5 – Pent(a)
6 – Hex(a)
7 – Hept(a)
8 – Oct(a)
9 – Non(a)
10 – Dec(a)
• CO2
• N2O
• B2H6
• CH4
• NH3
Naming
molecules from
their formulas
Use the Prefixes…
1 – mono
2 – Di
3 – Tri
4 – Tetr(a)
5 – Pent(a)
6 – Hex(a)
7 – Hept(a)
8 – Oct(a)
9 – Non(a)
10 – Dec(a)
• CO2
carbon dioxide
• N2O
dinitrogen monoxide
• B2H6
diboron hexahydride
• CH4
carbon tetrahydride
commonly known as “Methane”
• NH3
nitrogen trihydride
commonly known as “Ammonia”
Writing formulas
for molecules
from their names
Use the Prefixes…
1 – mono
2 – Di
3 – Tri
4 – Tetr(a)
5 – Pent(a)
6 – Hex(a)
7 – Hept(a)
8 – Oct(a)
9 – Non(a)
10 – Dec(a)
• Carbon monoxide
• Sulfur trioxide
• Silicon tetrachloride
• Diphosphorus pentachloride
• Tetraphosphorus triselenide
Writing formulas
for molecules
from their names
Use the Prefixes…
1 – mono
2 – Di
3 – Tri
4 – Tetr(a)
5 – Pent(a)
6 – Hex(a)
7 – Hept(a)
8 – Oct(a)
9 – Non(a)
10 – Dec(a)
• Carbon monoxide
• CO
• Sulfur trioxide
• SO3
• Silicon tetrachloride
• SiCl4
• Diphosphorus pentachloride
• P2Cl5
• Tetraphosphorus triselenide
• P4Se3
Practice naming
and writing
formulas
Use the Prefixes…
1 – mono
2 – Di
3 – Tri
4 – Tetr(a)
5 – Pent(a)
6 – Hex(a)
7 – Hept(a)
8 – Oct(a)
9 – Non(a)
10 – Dec(a)
• WARNING! Some of the
compounds listed below are
NOT covalent. Make sure you
don’t use prefixes when
naming them.
• Name these compounds: CBr4
, N2O5, MgF2 , SeS ,
• Write formulas for these:
Carbon disulfide, Disilicon
hexahydride, Potassium
carbonate, Dinitrogen
tetroxide