Naming Compounds
Names and Formulas
Writing Chemical Formulas
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Chemical Formula:
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1 – what elements
2 - ratios in compound
Metals(positive ions) written first
Polyatomic Ions:
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group of atoms that act as an element
has its own ionic charge
Always look on the Data Table for
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name and
ion charge
Ion Charge and the Formulas
of Ionic Compounds
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Law of Definite Proportions:
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a specific compound elements are always in
definite proportions; integers no decimals or
fractions
Ex: H2O – always 2 hydrogen atoms for one
oxygen atom
Ionic compounds:
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metal + non-metal
Electron(s) transferred
bonded by electrical force (opp. charges attract)
electrically neutral
Ion Charge and the Formulas
of Ionic Compounds
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Ionic compounds:
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metal + non-metal
Positive ion + negative
Cation + Anion
Formulas of Ionic Compounds
Use
Crossover Rule:
Ion Charge and the Formulas
of Ionic Compounds
Formulas for Ionic Compounds with
Polyatomic Ions:
 Use crossover rule but
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Polyatomic Ions --- MUST BE KEPT
TOGETHER
Use brackets around polyatomic groups if
there is more than 1
Ion Charge and the Formulas
of Ionic Compounds
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multivalent:
element with more than 1 possible ion charge;
 occurs only after atomic # 20 – Ca
 Are in Transition metals on PT
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Use crossover rule
When naming the CHARGE is written in
roman numerals ex. Iron(III)oxide
Naming Ionic Compounds
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Rules for Naming Ionic Compounds:
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Metal(pos) ion written 1st
name spelled same in lower case
non-metal ion written 2nd
given suffix “–ide”
Naming Ionic Compounds
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Naming Polyatomic Ions:
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pos. polyatomic ions written 1st
neg. polyatomic ions written 2nd; name of ion
not changed
Use the data table
Do Exercise #4
Naming Ionic compounds using the formula
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Example 1: Ag2SO4
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Silver is monovalent, so, no Roman Num. necessary
Look up SO4 on table – sulphate
Therefore, name is Silver sulphate
Example 2: Cu2O
 look at the total amt of charge on each half of formula:
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The neg side O for oxygen is monovalent – has charge of 2Therefore the pos side must have a charge of 2+
As there are 2 Cu, the charge on each Cu must be 1+
 (1+ plus 1+ equals 2+)
Therefore the name of the compound must be
 Copper(I) oxide
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(remember multivalents must use Roman Numerals in the name)
Naming Ionic compounds using the
formula
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Example 3: FeS
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Iron(Fe) is multivalent, so, Roman Num. necessary
Look up S on Periodic table – has a 2- charge
So, Fe must have a 2+ charge to balance
Therefore the name is Iron(II) sulphide
Example 4: Fe2(HPO4)3
 look at the total amt of charge on each half of formula:
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The neg side: eacg HPO4 has charge of 2There are 3 HPO4 the neg side must have a charge of 6- (3 x 2- = 6-)
As there are 2 Fe, the charge on each Fe must be 3+
 (3+ plus 3+ equals 6+)
Therefore the name of the compound must be
 Iron(III) monohydrogen phosphate
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(remember multivalents must use Roman Numerals in the name)
Naming Ionic compounds using the formula
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Try It:
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1
2
3
4
5
6
7
8
9
–
–
–
–
–
–
–
–
–
Ag3PO4
Al2(SO4)3
Fe2S3
CuCl
(NH4)2CO3
VCl3
Hg2CO3
CuSO4
(NH4)2S
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Answers:
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1
2
3
4
5
6
7
8
9
–
–
–
–
–
–
–
–
–
Silver phosphate
Aluminum sulphate
Iron(III) sulphide
Copper(I) chloride
Ammonium carbonate
Vanadium(III) chloride
Mercury(I) carbonate
copper(II) sulphate
Ammonium sulphide
Naming Ionic compounds using the formula
Do Exercise #5
 Do Handout: Writing formulas Quiz
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Do Handout: Formula Writing
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(exercise in Names -> Formulas)
(exercise in Names -> Formulas)
Do Handout: Inorganic Nomenclature
Test (may do as Test or Quiz)
Naming Ionic compounds using the formula
Hydrates
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When a crystal of an ionic compound is
grown by evaporation from aqueous solution,
frequently it is found that the crystal structure
will include water molecules
Molecules which include water molecules are
called HYDRATES
Use prefixes to tell how many water
molecules are attached;
Naming Ionic compounds using the
formula
Prefixes for Hydrates
mono
 di
 tri
 tetra
 penta
 hexa
 hepta
 octa
 nona
 deca
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1
2
3
4
5
6
7
8
9
10
Naming Ionic compounds using the
formula
Prefixes for Hydrates
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Examples:
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CuSO4*5H2O
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Copper(II)sulphate
pentahydrate
Zn(CH3COO)2*2H2O Zinc acetate dihydrate
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Ca(NO3)2*4H2O
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Calcium nitrate tetrahydrate
Do exercise #6 & #7
Naming Covalent Compounds
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Unlike Ionic compounds there are several
various combinations of elements possible.
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Ionic example: sodium and chlorine
always forms NaCl
It is the ONLY possible combination
This combination is called a formula unit; NOT
a molecule
Covalent example: carbon and oxygen
Naming Covalent Compounds
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Unlike Ionic compounds, Covalent compounds
has numerous possibilities in how the elements
can combine:
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Example: carbon and oxygen
Can form CO or CO2 or CO3
Each has unique properties:
CO will kill you while CO2 will not
You cannot all these variations carbon oxide
A different naming system is necessary
Naming Covalent Compounds
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Prefix naming system – use prefixes to name the
various covalent molecules
Note: these are molecules not formula units as
with Ionic compounds
Examples of naming covalent molecules:
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carbon and oxygen can form CO or CO2 or CO3
CO is named carbon monoxide
CO2 is named carbon dioxide
CO3 has a special name carbonate – a polyatomic
structure
Naming Covalent Compounds
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Prefixes indicates the number of the types of atoms in a molecule
mono
di
tri
tetra
penta
hexa
hepta
octa
nona
deca
1
2
3
4
5
6
7
8
9
10
Naming Covalent Compounds
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Rules for prefixes:
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1 - don’t use mono for the first element if there is only one;
2 - always use mono for second element if there is only one atom in the
molecule
3 - mono drops the 2nd “o” as in carbon monoxide
4 - second element ends with ‘ide’
5 – add the appropriate prefix according to number of atoms present in
molecule
Naming Covalent Compounds
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The name of the molecule always reflects the structure of the
molecule
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Example: P4O10 --- tetraphosphorus decaoxide
You can tell what the formula is by looking at the name;
or
You can tell what the name is by looking at the formula
This makes covalent compounds easy to name and easy to write the formula
Naming Covalent Compounds
 REMEMBER:
always determine
to see if the compound is
 IONIC or
 COVALENT
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Then follow the appropriate rules
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Do Exercise #8 & 9
Handout:
Nomenclature
Flow Chart
Naming Acids
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2 types of acids:
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1 -- has NO oxygen
name begins with ‘hydro’
ends with ‘ic’
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examples:
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HF – hydrogen fluoride
hydrofluoric acid
HCl – hydrogen chloride
hydrochloric acid
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Naming Acids
 2 -- has oxygen
 There are 2 types of acids WITH oxygen:
 One type the chemical name ends with “ite” as in hydrogen sulphite
 The other the chemical name ends with ”ate” as in hydrogen carbonate
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examples:
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Formula Chemical Name:
H2SO3 – hydrogen sulphite
sulphurous acid
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H2CO3 – hydrogen carbonate
 for both there is NO ‘hydro’ in the name
ous
”ate” becomes ic
 “ite” becomes
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carbonic acid