1. Chapter 9
Chemical Names and
Formulas
Section 9.1
Naming Ions
1

2. Monatomic Ions
Ionic compounds consist of a positive metal ion and a
negative nonmetal ion combined in a proportion such
that their charges add up to a net charge of zero.
NaCl – consists of one Na+ and one Cl-.
Monatomic ions consists of a single atom with a positive
or negative charge resulting from the loss or gain of one
or more valence electrons.
2

3. Monatomic Ions - Cations
Cations tend to lose valence electrons. (1+ charge – lose 1
electron, 2+ charge – lose 2 electrons, etc. )
When the metals in Groups 1A, 2A, and 3A lose electrons, they
form cations with positive charges equal to their group number.
The name of the cations of the Group 1A, 2A and 3A are the
same as the name of the metal, followed by the word ion or
cation.
Na+ is sodium ion, Ca2+ is calcium ion, Al3+ is aluminum ion.
3

4. Monatomic Ions - Anions
Nonmetals tend to gain electrons to form anions, so the
charge of a nonmetallic ion is negative.
The charge of any ion of a Group A nonmetal is
determined by subtracting 8 from the group number.
Group 7A form anions with a 1- charge (7-8 = -1)
Anion names start with the stem of the element name
and end in –ide.
Anion of fluorine is fluoride ion (F-), anion of chlorine is
chloride ion (Cl-)
4

5. Ions of Transition Metals
Many of the transition metals (Group 1B – 8B) form more
than one cation with different ionic charges.
Two methods are used to name these ions.
1. Stock System – a roman numeral in parentheses is
placed after the name of the element to indicate the
numerical value of the charge.
Fe2+ is iron(II) ion Fe3+ is iron(III) ion.
2. Classical – name of the element is used to form the
root name for the element.
Fe2+ is ferrous ion Fe3+ is ferric ion
5

6. Symbols and Names of common Metal Ions
Cu + Copper (I) ion Cuprous ion
Cu 2+ Copper (II) ion Cupric ion
Hg + Mercury (I) ion Mercurous ion
Hg 2+ Mercury (II) ion Mercuric ion
Fe 2+ Iron (II) ion Ferrous ion
Fe 3+ Iron (III) ion Ferric ion
Cr 2+ Chromium (II) ion Chromous ion
Cr 3+ Chromium (III) ion Chromic ion
Mn 2+ Manganese (II) ion Manganous ion
Mn 3+ Manganese (III) ion Manganic ion
Co 2+ Cobalt (II) ion Cobaltous ion
Co 3+ Cobalt (III) ion Cobaltic ion
Pb 2+ Lead (II) ion Plumbous ion
Pb 4+ Lead (IV) ion Plumbic ion
Sn 2+ Tin (II) ion Stannous ion
Sn 4+ Tin (IV) ion Stannic ion
Cd 2+ Cadmium ion
Zn 2+ Zinc ion
Ag + Silver ion
6

7. Polyatomic Ions
Polyatomic Ions are composed of more than one atom.
Sulfate ions (SO4
2-) is composed of one sulfur atom and
four oxygen atoms.
Polyatomic ions are a tightly bound group of atoms that
behave as a unit and carry a charge.
The names of most polyatomic anions end in –ite or –ate.
7

8. Common Polyatomic Ions
Charge 1 +
NH4
+ Ammonium
Charge 1 ─
ClO ¯ Hypochlorite OH ¯ Hydroxide
ClO2
¯ Chlorite CH3COO ¯ Acetate
ClO3
¯ Chlorate CN ¯ Cyanide
ClO4
¯ Perchlorate OCN ¯ Cyanate
lO2
¯ Iodite HSO3
¯ Bisulfite
lO3
¯ Iodate HSO4
¯ Bisulfate
lO4
¯ Periodate HCO3
¯ Bicarbonate
NO2
¯ Nitrite BrO3
¯ Bromate
NO3
¯ Nitrate MnO4
¯ Permanganate
8

9. Common Polyatomic Ions
Charge 2 ─
CO3
2− Carbonate CrO4
2− Chromate
O2
2− Peroxide Cr2O7
2− Dichromate
SO4
2− Sulfate C2O4
2− Oxalate
SO3
2− Sulfite SiO3
2− Silicate
S2O3
2− Thiosulfate
Charge 3 ─
PO3
3− Phosphite AsO3
3− Arsenite
PO4
3− Phosphate AsO4
3− Arsenate
BO3
3− Borate
Charge 4 ─
P2O7
4− Pyrophosphate
9

10. Section 9.2
Naming Ionic Compounds
10

11. Naming Binary Ionic Compounds
A binary compound is composed of two elements and
can be either ionic or molecular (covalent).
To name any binary ionic compound, place the cation
name first, followed by the anion name.
Cs2O is cesium oxide NaBr is sodium bromide
Cu2O is copper(I) oxide CuO is copper(II) oxide
11

12. Writing Formulas
Binary Ionic Compounds
Write the symbol of the cation and then the anion. Add
whatever subscripts are needed to balance the charges.
The positive charge of the cation must balance the
negative charge of the anion so that the net ionic charge
of the formula is zero.
K+ + Cl-  KCl
Ca2+ + Br -  CaBr2
Fe3+ + O2-  Fe2O3
Use the crisscross method – the numerical value of the
charge of each ion is crossed over and becomes the
subscript for the other ion.
12

13. Writing Formulas
Polyatomic Ionic Compounds
An –ate or –ite ending on the name of a compound
indicates that the compound contains a polyatomic anion
that includes oxygen.
Write the symbol for the cation followed by the formula
for the polyatomic ion and balance the charges.
Ca2+ + NO3
-  Ca(NO3)2
Sr2+ + SO3
2-  SrSO3
Li+ + CO3
2-  Li2CO3
Use the crisscross method – the numerical value of the
charge of each ion is crossed over and becomes the
subscript for the other ion.
13

14. Naming Polyatomic Ionic
Compounds
First recognize that the compound contains a polyatomic
ion.
State the cation first and then the anion
NaClO
sodium hypochlorite
(NH4)2C2O4
ammonium oxalate
Li2CO3
lithium carbonate
14

15. Section 9.3
Naming and Writing
Formulas for
Molecular Compounds
15

16. Naming Molecular Compounds
Binary ionic compounds are composed of the ions of two
elements, a metal and a nonmetal.
Binary molecular compounds are composed of two
elements, two nonmetals and they are not ions.
Binary molecular compounds are composed of
molecules, not ions, so ionic charges cannot be used to
write formulas or to name them.
In addition, when two nonmetallic elements combine,
they often do so in more than one way. (CO, CO2)
Prefixes in the names of binary molecular compounds
help distinguish compounds containing different
amounts of the same two elements. 16

17. Naming Molecular Compounds
The prefix in the name of a binary molecular compound
tells how many atoms of each element are present in
each molecule of the compound.
Prefix Number
mono- 1
di- 2
tri- 3
tetra- 4
penta- 5
hexa- 6
hepta- 7
octa- 8
nona- 9
deca- 10 17

18. Naming Molecular Compounds
The names of all binary molecular compounds end in
–ide.
CO is carbon monoxide
CO2 is carbon dioxide
If just one atom of the first element is in the formula, omit
the prefix mono-
•Name the elements in order listed in the formula
•Use prefixed to indicate the number of each kind of atom
•The suffix of the name of the second element is –ide.
N2O is dinitrogen monoxide
SF6 is sulfur hexafluoride. 18

19. Writing Formulas
Molecular Compounds
Use the prefixes in the name to tell you the subscript of
each element in the formula.
Then write the correct symbols for the two elements with
the appropriate subscripts.
Dinitrogen tetraoxide
N2O4
Diphosphorus trioxide
P2O3
19

20. Section 9.4
Naming and Writing
Formulas for
Acids and Bases
20

21. Naming Acids
Acid is a compound that contains one or more hydrogen
atoms and produces hydrogen ions (H+) when dissolved
in water.
When naming acids, the acid consists of an anion
combined with as many hydrogen ions as needed to
make the molecule electrically neutral.
The general chemical formulas of acids is HnX.
X is a monatomic or polyatomic anion
n is a subscript indication the number of hydrogen ions
combined with the anion.
21

22. Naming Acids
Three rules are used to name acids. The name depends
on the name of the anion and its suffix (-ide, -ite, -ate)
1. a. When the name of the anion ends in –ide, the acid
name begins with the prefix hydro-.
b. The stem of the anion has the suffix –ic and is
followed by the word acid.
H+ + Cl -  HCl
Hydrogen ion chloride ion hydrochloric acid
H+ + S2-  H2S
Hydrogen ion sulfide ion hydrosulfuric acid
22

23. Naming Acids
Three rules are used to name acids. The name depends
on the name of the anion and its suffix (-ide, -ite, -ate)
2. a. When the anion name ends in –ite, the acid name
is the stem of the anion with the suffix –ous,
followed by the word acid
H+ + SO3
2-  H2SO3
Hydrogen ion sulfite ion sulfurous acid
H+ + CIO2
-  HCIO2
Hydrogen ion chlorite ion chlorous acid
23

24. Naming Acids
Three rules are used to name acids. The name depends
on the name of the anion and its suffix (-ide, -ite, -ate)
3. a. When the anion name end in –ate, the acid name
is the stem of the anion with the suffix –ic followed by
the word acid.
H+ + NO3
-  HNO3
Hydrogen ion nitrate ion nitric acid
H+ + SO4
2-  H2SO4
Hydrogen ion sulfate ion sulfuric acid
24

25. Writing Formulas for Acids
Use the rules for writing the names of acids in reverse to
write the formula for acids.
Hydrobromic acid
Hydro indicates the bromide ion
HBr
Phosphorous acid
-ous indicates the phosphite ion
H3PO3
phosphoric acid
-ic and beginning with the anion name indicates the phosphate ion
H3PO4
25

26. Bases
A base is an ionic compound that produced hydroxide
ions (OH-) when dissolved in water.
Bases are named the same way as other ionic
compounds – the name of the cation is followed by the
name of the anion.
NaOH is sodium hydroxide
To write the formulas for bases, write the symbol for the
cation followed by the formula for the hydroxide ion.
(then use the crisscross method to write the formula as
you do as you do for any ionic compound)
Aluminum hydroxide – Al3+ + OH-  Al(OH)3
Ammonium hydroxide – NH4
+ + OH-  NH4OH
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