CHAPTER 5 NAMING COMPOUNDS
Background Information:
Counting Atoms
- The formula tells the elements that make up a compound and the number of atoms of each
element in the compound.
- The number of atoms is indicated by a subscript.
• Ex H2O
• H= 2
O=1
- When a subscript appears outside of a set of parentheses, multiply everything inside the
parentheses by the subscript.
• Ex Mg3(PO4)2
• Mg = 3
P=2
O=8
- A coefficient tells how many whole molecules or elements are present. It is located before the
formula or element and is multiplied through the whole formula.
• Ex 4Mg3(PO4)2
• Mg = 12
P=8
O = 32
•
- If there is more than one instance of an element in a formula then count the number of atoms for
each individually and add them together.
• Ex Na3COOH
• Na = 3
C=1
O=2
H=1
Determining bond typeA. Ionic bonds- bonds between a metal and a nonmetal – ex NaCl
B. Covalent bonds- bonds between two nonmetals - ex H2O
C. Metallic bonds-bonds between two atoms of same metal- ex Cu
D. Practice
1. Mg and F
2. Na and Br
7. H and H
3. O and Cl
4. Fe and Fe
8. H and Cl
5. Zn and Zn
6. O and F
STOP HERE and COMPLETE HOMEWORK
Writing ionic formulas
1. criss cross method is a easy way to determine the formula BUT you must
also understand why this method works!!!!
2. Guess what?
a. in order to complete the criss cross method you need to
know the oxidation number of the element
b. Practice
i.)
Na
+
Cl
=
Na CL
ii)
Mg
+
F
iii)
Ca
+
O
iv)
N
+
=
Mg F
=
Li
Ca O
=
Li N
c. why is lithium written before nitrogen?
The positive ion is called a cation and is always written first
The negative ion is called an anion and is written second.
** in other words the Cation (usually the metal) is ALWAYS written first
C. Transition metals work a little differently
a. how many valence electrons do transition metals have?
*because they vary we need to figure out and then write down their oxidation number
Recall – we figure out the oxidation number of a transition metal by looking at who
they are paired with
***helpful hint – the TOTAL charge must always = 0
b. sometimes we use use roman numerals or numbers to do this
I = one II = two III = three IV = four
c. practice
i.) Cr (+4)
+ O
=
Cr O
c. What is the charge/oxidation number on Iron?
ii) Fe (
)
+
O = Fe2O3
iii) Zn (+2)
+
Cl
=
Zn
what is the charge/oxidation number on nickel?
iv) Ni (
)
+
S
= NiS
Cl
v)
Mn (
)
+
O
=
MnO2
Rules for Naming Ionic Compounds
A. Binary Ionic Compounds (metals from Group 1 or 2) (ex: CaCl2)
1. Name the metal
2. Name the nonmetala. change ending to –ide
(calcium chloride)
3. Practice:
a. KCl
b. LiF
c. Na2O
B. Binary Ionic Compounds (transition metals)
(ex: Fe2O3)
1. Name the metal
2. Transition metals have more than one + charge (ex: iron can have +2 or
+3)
a. determine the charge of nonmetal
Fe
O
b. Figure out the - charge on “non-metal” side, then set the metal equal to the
+ charge
3. After the name of metal, write charge in roman numerals. (put in ( ) ).
Fe +3 = iron (III)
4. Name the nonmetal. Change ending to –ide
5. Fe2O3 = Iron(III)oxide
5. Practice:
a. CuO
b. ZnCl2
Mixed practice:
1. Na20
2. FeF3
3. BaI2
4. AgS
Naming covalent Compounds
1. Use same ending as most ionic compounds…….ide
1. Covalent Bonding requires Prefixes
*you cannot start any covalent compound with the word mono
PREFIX
Mono
Di
Tri
Tetra
Penta
Hexa
Hepta
Octa
Nona
Deca
NUMBER
1
2
3
4
5
6
7
8
9
10
a. prefixes tell you how many of each atom there are in the compound
2. Examples
a. H2O
b. BF3
c. N2O4
3. Practice
a. SiO2
b. CO2
c. CO
d. P2O5
C. Naming Compounds with polyatomics …… Poly = many
1. Certain ions are made of covalently bonded atoms that tend to stay together and
act as if they were single atoms
2. therefore bonds WITHIN polyatomic ions = covalent (talk later)
3. but they usually form ionic bonds with other atoms
Some of the common polyatomics and their charge
Ammonium
Acetate
Chlorate
Hydrogen carbonate
Hydroxide
Nitrite
Nitrate
Carbonate
Sulfate
Sulfite
Phosphate
NH4 +1
C2H3O2 -1
ClO3 -1
HCO3 -1
OH -1
NO2 -1
NO3 -1
CO3 -2
SO4 -2
SO3 -2
PO4 -3
4. Differert types of ployatomic compounds
a. (metal + polyatomic)
step one…..Name metal
-use roman numerals for transitions
step 2….. Name the poly.
-DO NOT CHANGE ENDING
b. (poly. + nonmetal)
step 1 …..Name poly.
(no ending changes)
step 2…..Name nonmetal.
change ending to –ide
c. (poly. + poly)
step 1…..Name the 1st poly.
Step 2…..Name the 2nd poly. -no ending changes
4. Practice:
a. NaHCO3
b. Mg(OH2)
c. Na2SO4
d. K2CO3
e Ca(ClO3)2
f. Sn(CH3COO)2
g. Ca(OH)2
h. K2CO3
i. MgSO4
j. CuSO4
k. Pb(OH)2
l. CuCO3
Naming Acids
When dissolved in water, certain molecules produce H+ ions. These substances are
called acids. An acid can be viewed as a molecule with one or more H+ ions
attached to an anion (negatively charged atom).
If the anion DOES NOT CONTAIN OXYGEN, the acid is named with the prefix
“hydro” and the siffix “ic” is attached to the root name for the element
EXAMPLE HCl dissolved in water = no oxygen therefore…….HYDROchlorIC acid
HCN disssolved in water = hydrocyanic acid
H2S dissolved in water = hydrosulfuric acid
If the anion DOES CONTAIN OXYGEN, the acid name is formed from the root name
of the central element of the anion with a suffix of “ic” or “ous”. When the anion
name ends in ate the suffix “ic” is used.
Example H2SO4 dissolved in water = the anion is sulfate so…….sulfuric acid
H3PO4 dissolved in water = the anion is phosphate so…. phosphoric acid
HC2H3O4 = anion is acetate so…………acetic acid
Example: H2SO3 = anion is sulfite so …….. sulfurous acid
HNO2 = anion is nitrite so……. Nitrous acid