Chemical Formulas and
chemical compounds
Unit 7
Nomenclature
Unit 7.1
Review of ions
Cation: A positive ion
Mg2+, NH4+
Anion: A negative ion
Cl-, SO42-
Predicting Ionic Charges
Group 1: Lose 1 electron to form 1+ ions
H+
Li+ Na+
K+
Predicting Ionic Charges
Group 2: Loses 2 electrons to form 2+ ions
Be2+
Mg2+
Ca2+
Sr2+
Ba2+
Predicting Ionic Charges
B3+
Al3+
Ga3+
Group 13: Loses 3
electrons to form
3+ ions
Predicting Ionic Charges
Carbon loses 4, but the metals
have multiple charges
Group 14: Lose 4
electrons or gain
4 electrons?
Predicting Ionic Charges
N3- Nitride
P3- Phosphide
As3- Arsenide
Group 15: Gains 3
electrons to form
3- ions
Predicting Ionic Charges
O2- Oxide
S2- Sulfide
Se2- Selenide
Group 16: Gains 2
electrons to form
2- ions
Predicting Ionic Charges
F1- Fluoride
Cl1- Chloride
Br1- Bromide
I1-
Iodide
Group 17: Gains 1
electron to form
1- ions
Predicting Ionic Charges
Group 18: Stable
Noble gases do not
form ions!
Predicting Ionic Charges
Groups 3 - 12: Many transition elements
have more than one possible charge.
Iron(II) = Fe2+
Iron(III) = Fe3+
Predicting Ionic Charges
Groups 3 - 12: Some transition elements
have only one possible charge.
Zinc = Zn2+
Silver = Ag+
Writing Ionic Compound Formulas
Example: Barium nitrate
1. Write the formulas for the cation and anion,
including CHARGES!
2. Check to see if charges are balanced.
3. Balance charges , if necessary, using subscripts. Use
parentheses if you need more than one of a polyatomic
ion.
Ba2+ ( NO3-) 2
Ba(NO3)2
Not balanced!
Writing Ionic Compound Formulas
Example: Ammonium sulfate
1. Write the formulas for the cation and anion,
including CHARGES!
2. Check to see if charges
are balanced.
3. Balance charges , if necessary, using subscripts. Use
parentheses if you need more than one of a polyatomic
ion.
( NH4
(NH4)2SO4
+)
2
SO42-
Not balanced!
Writing Ionic Compound Formulas
Example: Iron(III) chloride
1. Write the formulas for the cation and anion,
including CHARGES!
2. Check to see if charges are balanced.
3. Balance charges , if necessary, using subscripts. Use
parentheses if you need more than one of a polyatomic
ion.
Fe3+ Cl-
3
FeCl3
Not balanced!
Writing Ionic Compound Formulas
Example: Aluminum sulfide
1. Write the formulas for the cation and anion,
including CHARGES!
2. Check to see if charges
are balanced.
3. Balance charges , if necessary, using subscripts. Use
parentheses if you need more than one of a polyatomic
ion.
3+
Al
2
Al2S3
2S
3
Not balanced!
Writing Ionic Compound Formulas
Example: Magnesium carbonate
1. Write the formulas for the cation and anion, including
CHARGES!
2. Check to see if charges are balanced.
2+
Mg
MgCO3
CO32-
They are balanced!
Writing Ionic Compound Formulas
Example: Zinc hydroxide
1. Write the formulas for the cation and anion, including
CHARGES!
2. Check to see if charges are
balanced.
3. Balance charges , if necessary, using subscripts. Use
parentheses if you need more than one of a polyatomic
ion.
Zn2+ ( OH- ) 2
Zn(OH)2
Not balanced!
Naming Ionic Compounds
Cation first, then anion
Monatomic cation = name of the
element
Ca2+ = calcium ion
Monatomic anion = root + -ide
Cl- = chloride
CaCl2 = calcium chloride
Naming Ionic Compounds
(continued)
Metals with multiple charges (transition
metals)
 some metal forms more than one cation
 use Roman numeral in name
 PbCl2
 Pb2+ is cation
 PbCl2 = lead(II) chloride
Naming Molecular compounds
Unit 7.2
Naming Molecular Compounds
 Compounds between two nonmetals
 First element in the formula is named first.
 Keeps its element name
 Gets a prefix if there is a subscript on it
 Second element is named second
 Use the root of the element name plus the
-ide suffix
 Always use a prefix on the second element
 1 = mon(o)
 2 = di
 3 = tri
 4 = tetra
 5 = penta
 6 = hexa
 7 = hepta
 8 = octa
 9 = nona
 10 = deka
List of
Prefixes
Naming Binary Compounds
P2O5 = diphosphorus pentoxide
CO2 = carbon dioxide
CO = carbon monoxide
N2O =
dinitrogen monoxide
Practice – Write the Formula
Compound Name
Compound Formula
Carbon dioxide
Carbon monoxide
Diphosphorus pentoxide
Dinitrogen monoxide
Silicon dioxide
Carbon tetrabromide
Sulfur dioxide
Phosphorus pentabromide
Iodine trichloride
Nitrogen triiodide
Dinitrogen trioxide
Check next slide for answers
Answers – Write the Formula
Compound Name
Compound Formula
Carbon dioxide
CO2
Carbon monoxide
CO
Diphosphorus pentoxide
P2O5
Dinitrogen monoxide
N2O
Silicon dioxide
SiO2
Carbon tetrabromide
CBr4
Sulfur dioxide
SO2
Phosphorus pentabromide
PBr5
Iodine trichloride
ICl3
Nitrogen triiodide
NI3
Dinitrogen trioxide
N2O3
Practice – Name the Compounds
Compound Formula
Compound Name
N2O4
SO3
NO
NO2
As2O5
PCl3
CCl4
H2O
SeF6
Check next slide for answers
Answers – Name the Compounds
Compound Formula
Compound Name
N2O4
dinitrogen tetroxide
SO3
sulfur trioxide
NO
nitrogen monoxide
NO2
nitrogen dioxide
As2O5
diarsenic pentoxide
PCl3
phosphorus trichloride
CCl4
carbon tetrachloride
H2O
dinitrogen monoxide
SeF6
selenium hexafluoride
Naming acids
Acids have an H in front of the formula
HCl, HNO3, HI
Binary acids: Hydrogen and a nonmetal (HBr, HCl, HI)
use the prefix hydro and use the -ic ending on nonmetal
hydrobromic acid, hydrochloric acid, hydroiodic acid
Oxyacids: Hydrogen and a polyatomic ion (HNO3, H2SO3)
NO PREFIX
Change ate ending to -ic and ite endings to –ous
nitric acid, sulfurous acid
Write the formula
– Hydrosulfuric acid, phosphoric acid, chlorous acid
Answers:
– H2S
– H3PO4
– HClO2
Nomenclature Practice and molar
masses
Unit 7.3
Name the following
•
•
•
•
•
•
•
•
•
•
•
•
•
AgCl
ZnO
MgCl2
FeCrO4
KClO
CuSO4
As2O5
P4O10
H2CO3
Cu2S
HNO2
HBr
Cu(CH3COO)2
•
•
•
•
•
•
•
•
•
•
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•
•
Silver chloride
Zinc oxide
Magnesium chloride
Iron (II) chromate
Potassium hypochlorite
copper (II) sulfate
Diarsenic pentoxide
Tetraphosphorus decoxide
Carbonic acid
Copper (I) sulfide
Nitrous acid
Hydrobromic acid
Copper (II) acetate
Write the formula
•
•
•
•
•
•
•
•
•
Iodine trichloride
Zinc hydroxide
Potassium chlorate
Calcium nitrite
Hydrosulfuric acid
Sulfuric acid
Tin (II) sulfide
Iron (III) cynanide
Aluminum nitride
•
•
•
•
•
•
•
•
•
ICl3
Zn(OH)2
KClO3
Ca(NO2)2
H2S
H2SO4
SnS
Fe(CN)3
AlN
Calculating Formula Mass
Calculate the formula mass of carbon
dioxide, CO2.
12.01 g + 2(16.00 g) = 44.01 g
One mole of CO2 (6.02 x 1023 molecules)
has a mass of 44.01 grams
This is also called the molar mass (mass in 1 mol)
(It is also called the molecular mass for covalent bonds)
Calculate the formula mass
• Hydrofluoric acid
• HF
20 g/mol
• Magnesium chloride
• MgCl2 94.3 g/mol
• Iron (III) nitrate
• Fe(NO3)3 243.3 g/mol
Percent composition
• We can find the mass percent of each element in a
compound.
mass of element in compound
total mass of compound
.
x 100
Calculating Percentage Composition
Calculate the percentage composition
of magnesium carbonate, MgCO3.
Formula mass of magnesium carbonate:
24.31 g + 12.01 g + 3(16.00 g) = 84.32 g
 24.31 
Mg  
  100  28.83%
 84.32 
 12.01 
C 
  100 14.24%
 84.32 
 48.00 
O 
  100  56.93%
 84.32 
100.00
Using chemical formulas
Unit 7.4
Review
Find the formula mass of barium nitrate
Ba(NO3)2
137.33 + 2(14.01) + 6 (16) = 261.35 g/mol
Conversions
• How many grams are in 2.50 mol of oxygen gas?
• (2.50 mol) (32 g O2/ 1mole)
• 80.0 g
• How many moles are in 6.60 g of ammonium sulfate?
• (NH4)2SO4
• (6.60g)(1 mol/132.1 g)
• 0.0500 mol
• How many molecules are in 25.0 g of sulfuric acid?
• (25.0 g) (1 mol/98.1 g H2SO4) (6.02x1023 molecules/1 mol)
• 1.53 x 10
23
molecules
• How many hydrogen atoms are in 25.0 g of sulfuric acid
• 2(1.53 x 10
23
molecules)
Ibuprofen, C13H18O2 has a molar mass of 206.29 g/mol.
If a bottle of ibuprofen contains 33 g of it, how many moles of
ibuprofen are in the bottle and how many molecules are
there?
0.16 moles, 9.6 x 1022 molecules