Chapter 9
Naming Compounds and
Writing Formulas
Ionic Compounds;
Molecular Compounds
and Acids
Types of Compounds
CompoundFormed when atoms of two or more elements
combine CHEMICALLY.
Law of Definite ProportionsIn ANY CHEMICAL compound the elements
always combine in the same proportion by
mass.
This agrees with Dalton’s Atomic Theory
that atoms combine in small whole # ratios.
Molecular Compounds
Two Types of Compounds1. Molecular Compounds
2. Ionic Compounds
1. Molecular Compounds
Formed between 2 or more NONMETALS
(Covalent Bond- Share Electrons)
- Liquid or gas at room temp. and have
relatively low melting and boiling points.
Molecule
MoleculeNEUTRAL no charge, group of atoms that
act like a unit (one thing)
Molecules of a compound are all identical to
each other
Molecules of different compounds are
different.
Ex: CO2 (1C : 2 O); CO (1C : 1O)
Molecular Formula
Tells the number and kinds of atoms in a molecule
of a compound. (CO2 & CO)
Nonmetal + Nonmetal
Covalent Bond: Share Electrons
Diatomic molecules: 7 nonmetallic elements that
are always paired and exist a molecules NOT
atoms.
MEMORIZE: H O N Cl Br I F
Hydrogen H2; Oxygen O2; Nitrogen N2;
Chlorine Cl2; Bromine Br2; Iodine I2; Fluorine F2
Ionic Compounds
- Metal + Nonmetal
- Made up of IONS
- Relatively high melting and boiling points
- NEUTRAL (ion charges cancel out; total +
charge = total – charge)
ION
Atom or group of atoms that have an UNEQUAL
number of protons and electrons
(#p+ does NOT = #e-) have a + or – charge
Cations- atom or group of atoms with + charge
Metals
Lose electrons
When naming cations the name stays the same as the
element.
EX: Na+ = sodium ion; Al+3 = aluminum ion
Cation Charges
ionic charges of Group A metals (see front
of periodic chart)
ionic charges of Group B metals
(transitional metals) – see back of periodic
chart
Roman Numerals – are used to indicate the
charge of a transitional metal.
Examples: Copper I = Cu +; Copper II = Cu+2
Lead II = Pb+2; Lead IV = Pb+4
Anions
Atom or group of atoms with a – charge
Nonmetals
Gain electrons
When naming anions the ending changes
to “ide”
Ex: chlorine becomes chloride (Cl-);
oxygen becomes oxide(O-2); nitrogen
becomes nitride (N-3)
Polyatomic Ions
Tightly bound group of atoms that act as a unit
(one thing) and carry a charge.
Also called Radicals
Most end in “ite” or “ate”; “ite” ending has one less
oxygen than “ate” ending. Examples; chlorite
ClO2-1; chlorate ClO3-3
Except: hydorxide (OH-); cyanide (CN-);
ammonium (NH4+).
Hypo – means 1 less oxygen (hypodermic means
under the skin) hypochlorite ClOPer – means 1 more oxygen perchlorate ClO4-
Formula Unit (FU)
Lowest whole number ration on IONS in an ionic
compound.
- Ionic Compounds are NOT MOLECULES they are
called Formula Units.
Chemical Formula shows the kinds and number of
atoms in the SMALLEST UNIT of a compound.
The most positive element (metallic) is written first.
EX: H2O = 2 Hydrogen atoms + 1 Oxygen atoms
CO2 = 1 Carbon atom + 2 Oxygen atoms
Homework Questions
What are the differences between an ionic
compound and molecular compound? (3)
Answer: Ionic- made up of ions; metal +
nonmetal; High BP & MP; Formula Unit
Molecular- made up of nonmetals; share
electrons covalent bonds; usually liquids
or gases at room temp.; Molecules
Homework Questions
Why aren’t ionic compounds molecules?
Ionic Compounds are Formula Units (FU’s)
and molecules are made up of 2 or more
nonmetals
What is the smallest ratio of an ionic
compound called?
Formula Unit (FU)
Name the 7 diatomic elements and
write their formulas correctly.
Hydrogen; H2
Oxygen; O2
Nitrogen; N2
Chlorine; Cl2
Bromine; Br2
Iodine; I2
Fluorine; F2
Homework Questions cont.
Metals form + ions called ___________.
Nonmetals form - ions called _______.
What group of metals have more than one
possible charge?
Group B metals; transitional metals
What is a polyatomic ion?
A group of atoms that act as a single unit
and carry a charge.
Naming compounds and Writing Formulas
Binary compoundSimplest compound made up of 2 elements
Examples: [ Sodium chloride – NaCl ]
[iron II chloride – FeCl2 ]
(NAMING) 1.) element with the positive ionic charge is
written first. ( metals )
Group A Metals – metal name is written.
Example Na+ = sodium
Group B Metals ( Transitional ) – Roman Numeral
Indicates the charge.
Examples : Fe+2 = Iron II
Mercury I
Hg+ = ____________
Tin IV
Sn+4 = ____________
** Use the back of your periodic chart (Common Metal Ions with
more than 1 ionic charge!)
2.) element with the negative ionic charge is
written next. (
nonmetal
)
Change the ending of the nonmetal to ( ide )
Nonmetal marries the metal and changes its
name to “ide” like a bride.
Examples: chlorine – chloride
bromide
Bromine - ________________
oxide
Oxygen - ________________
USE THE RULES ABOVE TO NAME THE BINARY IONIC
COMPONDS BELOW:
Magnesium oxide 5.) FeCl3 ____________
Iron III chloride
1. MgO______________
Barium Sulfide
Tin IV bromide
2. BaS ______________
6.) SnBr4 ____________
Sodium nitride
phosphide
3. Na3N _____________
7.) K3P Potassium
____________
Copper I oxide
4. Cu2O _____________
8.) PbS
Lead
II sulfide
____________
WRITING FORMULAS
1.) write the ion for the metal first
Group A Metals –Examples: Lithium – Li +
+3
Al
Aluminum - ___
+2
Mg
Magnesium - ___
+1
Rb
Rubidium - ___
Group B Metals –
The Roman Numeral indicates the charge
Examples: Tin II – Sn+2
Copper I -
Cu+1
____
Hg+2
Pb+4
Mercury II - ____ Lead IV - ____
write the ion for the non-metal
Group VA, VIA, VIIA
The number of the charge = 8 – the groupA number
Examples: sulfide = 8 – 6 = 2
-3
P
phosphide = ______
I
Iodide = _____
ion = S-2
Cross-Over-Method
Place the charge number of the metal as the
subscript to the nonmetal and the charge number of
the nonmetal as the subscript to the metal.
You must reduce the charges if you can.
Examples:
Lithium Fluoride Li+ F- = LiF Magnesium Fluoride
+ -2
Potassium Sulfide K S = K2S
Mg+2 F- =MgF2
+
Copper I Chloride Cu Cl = CuCl
Aluminum Nitride Al+3N-3 = AlN Chromium III Sulfide Cr+3 S-2 = Cr2S3
USE THE RULES ABOVE TO WRITE FORMULAS
FOR THE BINARY IONIC COMPOUNDS:
Calcium Fluoride __________
Ca+2 F- = Rubidium Iodide ___________
Rb+ I- =
CaF2
RbI
+P3
Na
Sodium Phosphide ________ Strontium chloride__________
Sr+2 Cl- =
Na3P
SrCl2
Mercury I Oxide ___________
Hg+ O-2 = Tin II Sulfide______________
Sn+2 S-2 =
Hg2O
SnS
Fe+3 N-3 =
Iron III nitride _____________
Copper I Selenide___________
Cu+ Se-2 =
FeN
Cu2Se
Classwork and homework worksheet 2 & 3 Binary Ionic Compounds.
Ternary Compounds
Ionic and
Ternary Compounds are _________
Polyatomic Ion
contain a _____________________.
POLYATOMIC ION –
A group of atoms that act as a single unit and
carry a charge.
Polyatomic ions end in “ ite “ or “ ate“
EXCEPTIONS: (OH)- hydroxide
(CN)- cyanide
*only (+) poly atomic ions (NH4)+ ammonium
(PH4)+ phosphonium
(Naming) Rules are similar to Binary
ionic compounds.
Element with positive ionic charge is
cation )
written first. (
Group A Metals: name simply written Ex.
Ca2+ - calcuim
Group B Metals: need a roman numeral
Ex. Pb2+ _________
Lead II
2. Polyatomic ion (
radical ) written next.
Write the name as it appears on the back
of the Periodic Chart.
Ex. (C2H3O2)- acetate
(Cr2O7)2-
dichromate
Naming Examples: LiCO3 Lithium carbonate
Be(CN)2 Beryllium cyanide
Sn(SO4)2 Tin IV sulfate
USE THE RULES ABOVE TO NAME THE
TERNARY IONIC COMPOUNDS BELOW:
Magnesium sulfate
MgSO4 ___________________________
Sodium nitrate
NaNO3____________________________
Calcium carbonate
CaCO3 ___________________________
Sodium hydroxide
NaOH __________________________
Barium chlorite
Ba(ClO2)2 ________________________
Ternary Naming Continued
Iron III tartrate
Fe2(C4H4O6)3 __________________
Ammonium phosphate
(NH4)3PO4 ________________________
Copper I chromate
Cu2CrO4 __________________________
Mercury I nitrite
Hg(NO2) __________________________
aluminum sulfate
Al2(SO4)3 __________________________
Writing Ternary Ionic Formulas
Write the ion for the metal first.
– Group A Metals – Group # = charge
Ex. Calcium Group 2 = Ca +2
Rubidium Group 1 = Rb +1
Boron Group 3 = B +3
Group B Metals – The Roman Numeral
tells you the charge number.
Ex. Iron III Fe +3
Lead IV Pb+4
Mercury I Hg +1
Tin II Sn +2
Write the polyatomic ion next (USE
PARENTHESIS)
*Remember polyatomic ions end in
“ ite “ or “ ate “
except (OH)- hydroxide and (CN)- cyanide
Examples:
Sulfite SO3 -2
Carbonate CO3 -2
Phosphate PO4 -3
Nitrite NO2 -
Cross-Over-Method
write the charge number of the metal as
the subscript of the polyatomic ion. (You
MUST use PARENTHESIS if the subscript
is 2 or greater but DO NOT use
Parenthesis if the subscript is 1)
2. write the charge number of the
polyatomic ion as the subscript of the
metal. *You must reduce if you can but
NEVER change the polyatomic ion!! DO
NOT TOUCH THE POLYATOMIC ION !!
DO NOT CHANGE THE
DO NOT TOUCH THE POLYATOMIC ION
DO NOT CHANGE THE
FORMULA OF THE POLYATOMIC ION !!
Examples:
Magnesium nitrate Mg+2 NO3- = Mg(NO3)2
Aluminum sulfate Al+3 SO4-2 = Al2(SO4)3
Iron II sulfite Fe+2 SO3-2 = FeSO3
Iron III sulfite Fe+3 SO -2 = Fe (SO )
3
2
3 3
Tin IV nitrate
Sn+4 NO3- = Sn(NO3)4
USE THE RULES ABOVE TO WRITE TERNARY
FORMULAS FOR THE COMPOUNDS
+1;-2 (NH4)2S
Ammonium sulfide __________________
+1;-2 Ag2CrO4
Silver chromate ____________________
+3;-2 Fe2(C4H4O6)3
Iron III tartrate _____________________
+2;-1 Be(OH)2
Beryllium hydroxide ________________
aluminum oxalate
+3;-2
Al2(C2O4)3
_________________
+1;-1 CuCN
Copper I cyanide ___________________
+2;-2 NiCO3
Nickel carbonate ___________________
Molecular Compounds
Writing names and Formulas
Molecular Compounds
Made up of 2 or more NONMETALS (NO
METALS or IONS)
Share electrons when bonding
Sharing Electrons is called COVALENT
BONDING
The smallest unit of a molecular
compound is called a MOLECULE.
(NAMING) To write the name, write 2 words
1.) the non-metal closest to the metals on
the periodic chart is written first.
2.) Prefixes are used to tell how many
atoms of each element are in the
compound.
–1
–2
–3
–4
–5
mono
di
tri
tetra
penta
6 hexa
7 hepta
8 octa
9 nona
10 deca
Exception: don’t write mono- if there is
only one of the first element.
3.) The second element always uses a
prefix and ends in “ _ide ”.
4.)No double vowels when writing
names (oa, oo)
Ex. CO carbon monoxide
CO2 carbon dioxide
P2O5 diphosphorus pentoxide
Name These
N2O
Dinitrogen monoxide
NO2
Nitrogen dioxide
Cl2O7
Dichlorine heptoxide
CBr4
Carbon tetrabromide
SiO2
silicon dioxide
P2O3
Diphosphorus trioxide
(FORMULA WRITING)
NO CRISS CROSSING
Examples: Phosphorous pentachloride - PCl5
Dinitrogen trisulfide – N2S3
NO3
Nitrogen trioxide _________
CF4
carbon tetrafluoride _______
I2Cl10
Diiodine decachloride _____
PI3
phosphorous triiodide ______
SBr6
Sulfur hexabromide _______
NF5
nitrogen pentafluoride ______
P2S3
Diphosphorous trisulfide ____
CBr4
carbon tetrabromide ______
Acids
Writing names and Formulas
Acids
Compounds that give off hydrogen ions
when dissolved in water.
Must have H in them.
will always be some H next to an anion.
The anion determines the name.
Naming acids
If the anion attached to hydrogen is ends
in -ide, put the prefix hydro- and change ide to -ic acid
HCl - hydrogen ion and chloride ion
hydrochloric acid
H2S hydrogen ion and sulfide ion
hydrosulfuric acid
Naming Acids
If the anion has oxygen in it
it ends in -ate or -ite
change the suffix -ate to -ic acid
HNO3 Hydrogen and nitrate ions
Nitric acid
change the suffix -ite to -ous acid
HNO2 Hydrogen and nitrite ions
Nitrous acid
Name these
HF Hydrofluoric acid
H3P Hydrophosphoric acid
H2SO4 sulfuric acid
H2SO3 sulfurous acid
HCN hydrocyanic acid
H2CrO4 chromic acid
Writing Acid Formulas/Naming
Hydrogen will always be first
name will tell you the anion
make the charges cancel out
Starts with hydro- if no oxygen in the acid, -ide
ending becomes –ic
Ex. HCl = hydochloric acid
no hydro, -ate ending from polyatomic ion
becomes -ic, H2SO4 = sulfuric acid
-ite ending becomes –ous, H2SO3 = sulfurous
acid
Write formulas for these
hydroiodic acid
acetic acid
HI
HC2H3O2
carbonic acid
H2CO3
phosphorous acid
hydrobromic acid
H3PO3
HBr