Chemical Names and
Formulas
Molecules
A molecule is the smallest electrically neutral unit of a
substance that still has the properties of the
substance.
1. Monatomic - consist as a single atom (Ex: Noble gases)
He
2. Diatomic molecule -7 exist in nature “BrINCl HOF”
(means 2) atoms
Br2 I2 N2 Cl2 H2 O2 F2
3. Triatomic molecule ( Ex: O3 - ozone)
Chemical Formula: shows the kinds
and numbers of atoms in the smallest
representative unit of the substance
(formula unit)
H2 O
H2O2
What’s the difference between these two formulas?
When you change the subscripts the formula no
longer represents that compound.
REMEMBER!!!!
H – Element symbol always begins with
a capital letter
Na – If symbol has two letters, the second
letter is always lowercase
Chemical Formulas
How to read formulas:
H2O =
2 hydrogen atoms
1 oxygen atom
Ca(OH)2 – Number outside the parenthesis
distributes to inside the parenthesis
1 calcium atom
2 oxygen atoms
2 hydrogen atoms
Explain the following:
MgCl2 – What elements are present? How many?
Mg - 1
Cl - 2
Pb(NO3)2 – What elements are present? How
many?
Pb - 1
N- 2
O- 6
Ionic Charges of Representative Elements
1A
Li+
Na+
K+
Rb+
Cs+
2A
3A
Be2+
Mg 2+ Al3+
Ca 2+
Sr 2+
Ba 2+
4A
5A
N3P3As3-
6A
7A
O2- FS2- ClSe2- BrI-
8A
Oxidation Numbers – how many electrons an atom
would gain or lose to follow the octet rule
(also called its charges)
+1
+2
+3
-3
-2
-1
Charges of Transition Metals
These transition metals have more than one
charge:
Cr2+ or 3+
Cu+ or 2+
Mn2+ or 3+
Sn2+ or 4+
Fe2+ or 3+
Pb2+ or 4+
Co2+ or 3+
Ni2+ or 3 +
Hg1+ or 2+
Au1+ or 3 +
Sc2+ or 3+
Hg1+ or 2 +
I. Writing Formulas for
Binary Ionic Compounds
Rules:
1. Write symbol and charge for both
cation and anion.
2. Crisscross charges, drop the charge
and write as subscripts.
3. CHECK!! The formula must be in the
lowest possible ratio.
The cation is always written first!
Example Problems
Write formulas for these compounds:
calcium iodide
+2
Ca 1
I
CaI2
2
Tin (IV) oxide
+4
Sn 2
O
-2
4
Sn2O4 SnO2
White Board Practice
Aluminum sulfide
+3
Al 2
-2
S
Al2S3
3
Beryllium Oxide
+2
Be2
-2
O2
Be2O2 BeO
II. Naming Binary Ionic Compounds
1.) Use the name of the cation.
****Use Roman Numerals if
Transition Metal.
2.) Name the anion and change
ending to -ide.
Naming Binary Ionic Compounds
+2
+4
-1
-2
SnS2
Find Sn
Where is it located?
Use Roman Numerals
Tin(IV)Sulfide
WHITE BOARD practice problems
A.) KCl
B.) CuBr2
C.) AlF3
D.) MgO
E.) MnI2
+3
Al
-3
P
White Board Practice
1.)
+
K
-2
S
2.)
+3
Al
I
3.)
+
Ag
-2
O
4.)
+2
Ni
-2
O
+4
5.) Pb
-2
O
Polyatomic Ions
• Tightly bound groups of atoms that behave
as a unit and carry a charge.
Examples:
Ammonium
NH4+
Cyanide
CN-
Sulfite
SO32-
III. Writing Formulas for Ternary
Ionic Compounds
A. Contain a polyatomic ion
B. Same rules as for binary ionic compounds.
• Name the cation
***Use a Roman numeral if necessary
–Name the anion (change ending to –ide)
Polyatomic ions will stay the same!!
Use parenthesis if there is more than one
polyatomic ion
• Boron acetate
B3+
C2H3O2-1
• Magnesium Dichromate
Mg+2
Cr2O7-2
White Board Practice Problems
Write formulas for the following
ternary ionic compounds:
a.
b.
c.
d.
Calcium Carbonate
Barium Nitrite
Potassium Sulfate
Magnesium Phosphate
White Board Practice Problems:
• Name the following ternary ionic
compounds:
a.
b.
c.
d.
e.
f.
NaCN
NH4ClO
Li2SO3
CaC2O4
Al(OH)3
Sn3(PO4)2
V. Rules for Naming Covalent
Molecules
1. Prefixes are
used to show how
many atoms of
each element are
present in the
molecules
Prefixes used for Naming
Binary Covalent Compounds
Rules for Naming Covalent
Molecules
2. Second element is written with an –
ide ending.
***All binary compounds, both ionic and covalent
end in –ide.
3. The vowel at the end of the prefix is
dropped when the name of the
element begins with the same vowel.
Ex: monoxide, not monooxide
Rules for Naming Covalent
Molecules
4. Mono is omitted if there is just a single
atom on the first element in the name.
Ex: CO2
carbon dioxide not monocarbon dioxide
Naming Binary Covalent
Molecules
1.) CO
2.) SO2
3.) N2O
4.) CCl4
5.) N2O5
6.) NO4
7.) OF2
Writing Formulas for Binary
Covalent Molecules
Write the formulas for the following
compounds.
1. carbon monochloride
2. nonacarbon tetrachloride
3. heptabromine dioxide
4. phosphorus trichloride
5. octanitrogen pentafluoride
Ionic vs. Covalent
Are the following compounds ionic or covalent?
a. H2O
b. Sodium chloride
c. CuSO4
d. CO
e. Lithium hydroxide
f. dinitrogen tetraoxide
g. FeS
h. Cobalt (III) chloride
i. H2S
j. PF3
Naming Acids
• 1. All acids begin with H
• 2. If it is just H and another element,
the name begins with “Hydro” the
other element with its suffix changed
to “ic”
• HCl- Hydrochloric Acid
• HI- Hydroiodic Acid
• H2S- Hydrosulfuric Acid
Naming Acids (Cont.)
• 3. If the acid contains a polyatomic ion,
you only change the name of the
polyatomic ion
• ate goes to ic
• ite goes to ous
• H2SO4- Sulfuric Acid
• H2SO3- Sulfurous Acid
Naming Acids
•
•
•
•
•
•
HCl
H2SO4
HNO2
HC2H3O2
H3PO3
H2CO3
Relay Challenge
1.) How many atoms of fluorine are present in CF4?
2.) How many atoms of carbon are present in CF4?
3.) What is the formula for carbon monoxide?
4.)What is the formula for lithium chloride?
5.) What is the formula for the compound formed by iron (II) and carbonate ions?
6.) What is the formula for aluminum hydroxide?
7.) What is the formula for lead (IV) oxide?
8.) What is the formula for magnesium nitrate?
9.) What is the name of the compound: NH3? CCl4?
10.) What is the cation in iron (II) oxide?
11.) What is the name of the compound N2O2? H2O2?
12.) What is the formula for sulfur trioxide?
13.) What is the formula for dinitrogen tetrafluroide?
14. )What prefix is used to represent ten?
15.) How do you know a compound is covalent when looking at the chemical formula?
16.) Using the ion pairs listed, write the correct chemical formula that the ions would form:
a. Cr+3 I- =
b. Cu+2 O-2 =
c. Li+ S-2 =
17.) What is the oxidation number for iron (II) in iron (II) oxide?
18. Write the names for the compound FeO and Fe2O3. Justify why the names you wrote are
correct.
19.) What are the seven diatomic elements?
20.) What is the name of the compound Si2Br6?
21.) Write the formula for diboron hexahydride.
22.) Write the formula for oxygen gas.