Bell Ringer
 Draw
the Molecule & give the
Formula for:
– Carbon and 2 Sulfurs
– Hydrogen, Oxygen, and Chlorine
– Carbon, two Chlorines, 2 Fluorines
– Phosphorus, Hydrogen, Sulfur
Molecular Compounds:
Formulas & Naming
Ch 6.3b - Covalent Bonds
Describing Molecular
Compounds

What information do the name and formula of
a molecular compound provide?
– Ionic Bonds (Ionic Compounds) -
Describing Molecular
Compounds

What information do the name and formula of
a molecular compound provide?
– Ionic Bonds (Ionic Compounds) Name – Type of elements in the compound
 Formula – Ratio/Number of atoms of each
element in the compound.

Describing Molecular
Compounds
 Covalent Bonds (Molecular
Compounds)
– Name & Formula - the type and
number of atoms in a molecule of
the compound.
Naming Molecular Compounds
Naming Order:
 Step 1:
– Element farthest to the left  named 1st.
Most Metallic
 Elements in the same group  more metallic element
is closer to the bottom of the group.
 Name does not change! (just like in ionic)
– Formulas are written same way
– Example:

Sulfur is named before chlorine  SCl2

Naming Molecular Compounds

Exception: Oxygen & Halogens
–
–
Oxygen comes 2nd when combined
with lower-electronegativity halogens
(Group 17)
Example: ClO2 (electronegativity: Cl =
3.0; O = 3.5)
Naming Molecular Compounds

Step 2:
– Second element  “ide” ending (like the anion
in an ionic compound)

Examples:
–
–
Chlorine  chloride
Oxygen  oxide
Naming Molecular Compounds

Step 3:
–
Add prefixes to elements names to specify the
number of atoms of each element in the
compound.

mono - one
 di - two
 tri - three
 tetra - four
 penta - five

hexa - six
 hepta - seven
 octa - eight
 nona - nine
 deca - ten
Naming Molecular Compounds
Prefixes:
• mono - one
• di - two
• tri - three
• tetra - four
• penta - five
Example:
N2O 
 Dinitrogen monoxide

N4O5 
 Tetranitrogen pentoxide

Naming Molecular Compounds
 Exception
to Step 3–
– Only one atom of the 1st element = NO
PREFIX!
 Carbon monoxide
 CO2  Carbon dioxide
 SO10  Sulfur decaoxide
 CO
Naming Molecular Compounds
More Examples:

– Dinitrogen
pentachloride
 N2Cl5

– Dinitrogen
pentoxide
 N2O5

– Pentaphosphorous
hexachloride
 P5Cl6

– Sulfur decaoxide
 SO10
Writing Molecular Formulas

Step 1:
– Write the element symbols (in order)

Step 2:
– Prefixes values  subscripts

No prefix = 1 atom (no subscript)
– Only applies to 1st element in the formula
Writing Molecular Formulas
 Examples:
– Diphosphorus Pentoxide  P2O5
– Silcon Dioxide  SiO2
– Carbon Tetrachloride  CCl4
– Trineptunium Octoxide  Np3O8
You Try
 Give
the formula for:
– Oxygen Difluoride 
– Phosphorus Tribromide 
– Trisilicon Tetranitride 
 Give the Name
– NO2 
– N2O3 
– SO3 
for:
You Try - Answers
 Give
the formula for:
– Oxygen Difluoride  OF2
– Phosphorus Tribromide 
– Trisilicon Tetranitride 
 Give the Name
– NO2 
– N2O3 
– SO3 
for:
You Try - Answers
 Give
the formula for:
– Oxygen Difluoride  OF2
– Phosphorus Tribromide  PBr3
– Trisilicon Tetranitride 
 Give
the Name for:
– NO2 
– N2O3 
– SO3 
You Try - Answers
 Give
the formula for:
– Oxygen Difluoride  OF2
– Phosphorus Tribromide  PBr3
– Trisilicon Tetranitride  Si3N4
 Give
the Name for:
– NO2 
– N2O3 
– SO3 
You Try - Answers
 Give
the formula for:
– Oxygen Difluoride  OF2
– Phosphorus Tribromide  PBr3
– Trisilicon Tetranitride  Si3N4
 Give
the Name for:
– NO2  Nitrogen Dioxide
– N2O3 
– SO3 
You Try - Answers
 Give
the formula for:
– Oxygen Difluoride  OF2
– Phosphorus Tribromide  PBr3
– Trisilicon Tetranitride  Si3N4
 Give
the Name for:
– NO2  Nitrogen Dioxide
– N2O3  Dinitrogen Trioxide
– SO3 
You Try - Answers
 Give
the formula for:
– Oxygen Difluoride  OF2
– Phosphorus Tribromide  PBr3
– Trisilicon Tetranitride  Si3N4
 Give
the Name for:
– NO2  Nitrogen Dioxide
– N2O3  Dinitrogen Trioxide
– SO3  Sulfur Trioxide