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SIMPLY PUT, THE ART OF WRITING FORMULAS AND
NAMING CHEMICALS
CHEMICAL NOMENCLATURE
Writing Formulas• Binary ionic compounds• Ternary ionic compounds• Binary molecular compounds• Acids
Ionic Compounds• Composed of oppositely charged ions• Positive ion is a cation• Negative ion is an anion• Cations attract anions until the net
(overall) charge on the formula unit is zero
Properties of Ionic Compounds
• Usually solid at room temperature
• Are brittle and break under stress
• Usually soluble in water• Conduct when melted or
dissolved• Have high melting points
Binary Ionic Compounds• Contain a metal, written first, always positive,
from left of stairs on the periodic table (it may sometimes have a roman numeral for its charge
• Contain a nonmetal, written second, always negative, from the right of stairs on the periodic table, ends in -ide
• The oppositely charged ions attract each other until the net charge is 0.
Binary Ionic Formulas
Calcium oxide (metal / non-metal) Find calcium and its charge Ca+2
Find oxide and its charge O-2
To complete the formula, the charges must be completely balanced for a net charge of zero. Ca+2 O-2
The formula is: CaO
Another formula:
Aluminum sulfide (metal / nonmetal)
Find aluminum and its charge Al+3
Find sulfide and its charge S-2
To complete the formula, use the crisscross method and drop the signs:
Al+3 S-2
The formula is: Al2S3
Another one:• Copper (II) nitride (roman numeral tells
the charge!!!!!! It could be a +2 or a +1)• So Cu+2 for the first ion• And N-3 for the second ion• Cu3N2 is the resulting formula
Try these:
• Lithium sulfide Li2S
• Magnesium nitride Mg3N2
• Barium oxide BaO• Copper (II) bromide CuBr2
• Manganese (IV) oxide Mn2O4 = MnO2
• Iron (III) chloride FeCl3• Calcium selenide CaSe
Ternary Ionic Compounds• Consist of three or more elements. • Contain at least one polyatomic ion
which is a group of atoms with a charge such as sulfate, SO4
-2.
• Polyatomic ions usually end in -ate, -ite and sometimes -ide as in cyanide and hydroxide and are on the back of the periodic table.
Ternary Ionic Formulas
Lithium nitrate (metal / polyatomic ion)
Find lithium and its charge Li+1
Find nitrate and its charge NO3-1
To complete the formula, the charges must be completely balanced for a net charge of zero. (criss-cross, drop +/-)
The formula is: LiNO3
Another formula:Calcium nitrate (metal / polyatomic ion)
Find calcium and its charge Ca+2
Find nitrate and its charge NO3-1
To complete the formula, use the crisscross method and drop the signs. If the polyatomic ion has an added subscript, use parentheses around it.
(NO3)2
The formula is: Ca(NO3)2
Try these:
Potassium chlorate KClO3
Strontium nitrate Sr(NO3)2
Copper (II) sulfate CuSO4
Rubidium phosphate Rb3PO4
Aluminum chromate Al2(CrO4)3
Iron (III) cyanide Fe(CN)3
Ammonium sulfide (NH4)2S
Binary Molecular Compounds
• Contain two nonmetals• Nonmetals are located to the right of
the stairs on the periodic table• They share electrons in a covalent
bond to form molecules.
Properties of Molecular Compounds
• Usually gases at room temperature
• Are soft solids under stress• Usually soluble in water• Do not conduct when melted
or dissolved• Have low melting points
Binary Molecular Formulas
Dinitrogen pentoxide (non-metal / non-metal)
The prefix for each non-metal tells how many atoms of each element are present in the formula. It gives the subscript.
“di” means a subscript of 2 after nitrogen N2
“pent” means a subscript of 5 after oxygen O5
The formula is: N2O5
Try these:
Dichlorine heptoxide Cl2O7
Diphosphorous trioxide P2O3
Carbon tetrabromide CBr4
Dinitrogen tetrahydride N2H4
Carbon disulfide CS2
Boron trichloride BCl3
Naming Compounds These are the types:
A) Binary Ionic Compounds Metal with one possible charge Metal with two or more possible charges
B) Ternary Compounds
C) Binary Molecular Compounds
D) Acids
Binary Ionic Compounds (with fixed oxidation state on metal)• the metal has one possible charge and is
combined with a nonmetal
• Step #1: Name of Element with Positive Charge
• Step #2: Add Name of Negative element modifying ending to “ ide ”
Examples - Binary Ionic with one possible charge on the metal
• Al2S3 aluminum sulfide
• CaBr2 calcium bromide
• Mg3N2 magnesium nitride
• NaCl sodium chloride
Binary Ionic Compounds (with variable oxidation state on the metal)• the metal with several possible charges and is
combined with a nonmetal
• Step #1: Name of Element with Positive Charge followed by the Roman numeral for its charge
(I, II, III, IV, V, VI, VII, VIII, IX, X)
• Step #2: Add Name of Negative element modifying ending to “ ide ”
Examples - Binary Ionic with several possible charges on the metal
• CuCl2 copper (II) chloride
• CuCl copper (I) chloride
• Fe3N2 iron (II) nitride
• VBr5 vanadium (V) bromide
Ternary Ionic Compounds
• Step #1: Write name of the ion having positive charge. If it is a metal, check to see if it has fixed or variable charge. If variable, it must have a roman numeral!
• Step #2: Add name of the negative polyatomic ion WITHOUT changing its ending.
Examples of Ternary Ionic Compounds
• Zn (NO3)2 zinc nitrate
• Cs C2H3O2 cesium acetate
• Cr SO4 chromium (II) sulfate
• NH4 Cl ammonium chloride
• (NH4)2 SO3 ammonium sulfite
Additional Examples – Roman Numerals
• Fe (ClO3)3 Iron (III) chlorate
• Cu(NO3)2 Copper (II) nitrate
• Mn SO4 Manganese (II) sulfate
Review of all Ionic Compounds
Name the following ionic compounds:
BaS barium sulfide
K2SO4 potassium sulfate
PbO lead (II) oxide
Cu(NO3)2 copper (II) nitrate
AlN aluminum nitride
(NH4)2CrO4 ammonium chromate
Binary Molecular Compounds• Consist of two nonmetals• Write the name of the first element then the
second element, changing its ending to –ide.• Place prefixes in front of each element, indicating
the number of atoms of each element in the formula. One exception, never use mono- in front of the name of first element.
CO2 CO
carbon dioxide carbon monoxide
• The list of prefixes is on the back of your periodic table!!!
• Check it out!
Examples of Binary Molecular
• CBr4 carbon tetrabromide
• Cl2O7 dichlorine heptoxide
• N2O5 dinitrogen pentoxide
Formulas for Acids• Hydrosulfuric acid (hydro- tells you it is
binary!, sulf tells the second part) H+1 with S-2 and the formula is H2S
• Sulfuric acid ( ternary, no hydro, ic ending tells sulfate) H+1 and SO4
-2 combine for H2SO4
• Sulfurous acid (ternary, no hydro, ous tells sulfite) H+1 and SO3
-2 combine for H2SO3
Properties of Acids• Are corrosive - will cause burns• React with metals• Neutralize bases• Dissolve in water• Have a pH less than 7 on the pH scale• Taste sour like a lemon
Try These!Hydrochloric acid __________________
Chloric acid __________________
Chlorous acid __________________
Hypochlorous acid__________________
Perchloric acid __________________
Naming Acids• Acids start with hydrogen and are followed by an anion.
Use the root of the anion and change it in the following manner:
• Anion ending “ide” start with “hydro” root of anion followed by “ic” acid
HCl hydrochloric acid• Anion ending “ate” start with root of anion, followed by “ic”
acid
HClO3 chloric acid
• Anion ending “ite” start with root of anion, followed by “ous” acid
HClO2 chlorous acid
Examples of Naming Acids• H2Se hydroselenic acid
• H2SO3 sulfurous acid
• HNO3nitric acid
Examples of Naming Acids• HBr hydrobromic acid
• HClO4 perchloric acid
• HClOhypochlorous acid
Try These!
• H2S __________________
• H2SO4 __________________
• H2SO3 __________________
PROBLEM SOLVING• In this chapter you will have to solve the
following problems:
1. Find the percent composition of a material
2. Determine the empirical formula (simplest)
3. Determine the molecular formula (actual)
Acids: Know these!!!!• HCl• HNO3
• H2SO4
• H3PO4