Chapter 9
Chemical Names and Formulas
9.1 Naming Ions
9.2 Naming and Writing Formulas for Ionic Compounds
9.3 Naming and Writing Formulas for Molecular Compounds
9.4 Naming and Writing Formulas for Acids and Bases
Created by B. Shia 11-07
9.1 Naming Ions
Monatomic Ions:
How are the charges of Group A metal and
nonmetal ions related to their positions in the
periodic table?
Monatomic ions consist of a single atom with a
positive or negative charge resulting from the
loss or gain of one or more valence electrons,
respectively.
Monatomic Ions
Cations
When the metals in Groups 1A, 2A, and 3A lose
electrons, they form cations with positive charges equal
to their group number.
The names of the cations of the Group 1A, Group 2A,
and Group 3A metals are the same as the name of the
metal, followed by the word ion or cation.
Monatomic Ions
These elements have
ionic charges that can be
obtained from their group
numbers
Monatomic Ions
Anions
The charge of any ion of a Group A
nonmetal is determined by
subtracting 8 from the group
number.
Anion names start with the stem of
the element name and end in -ide.
These Group A elements form
anions.
Monatomic Ions
Monatomic Ions
Ions of Transition Metals
How are the charges of some transition metal ions
determined?
The charges of the cations of many transition metal ions
must be determined from the number of electrons lost.
Monatomic Ions
There are two methods are used to name the ions of transition
metals: the Stock system and the classical method
In the Stock system, a Roman numeral in parentheses is
placed after the name of the element to indicate the
numerical value of the charge. (Cu+ is copper (I) ion)
In an older less, useful method, the classical name of the
element is used to form the root name for the element. (Cu+
is cuprous ion)
Conceptual Problem 9.1
a) K+, cation, potassium ion
b) I-, anion, iodide ion
c) S2-, anion, sulfide ion
d) Pb4+, cation, lead (IV) ion
Polyatomic Ions
What are the two endings of the names of
most polyatomic ions?
Some ions, called polyatomic ions, are
composed of more than one atom.
The names of most polyatomic anions end
in -ite or -ate.
Polyatomic Ion
These models show the structures of four common
polyatomic ions.
Polyatomic Ions
Names and formulas
of some common
polyatomic ions
Know nitrate, hydroxide, sulfate,
carbonate, phosphate, ammonium;
possibly acetate
9.1 Section Quiz
1. When metals from groups 1A, 2A, and 3A
form cations, the charge on the ion is equal to
a. 8 minus the group number.
b. the group number minus 8.
c. the period number.
d. the group number.
9.1 Section Quiz
2. Which of the following are positively charged
polyatomic ions?
–(I) ammonium ion
–(II) perchlorate ion
–(III) ferric ion
a) I only
b) II only
c) III only
d) I and III
9.1 Section Quiz
3. If the name of an ion ends in -ite or -ate, the ion is a
a) polyatomic cation.
b) polyatomic anion.
c) transition metal cation.
d) monatomic anion.
9.2 Naming and Writing Formulas for Ionic Compounds
Binary Ionic Compounds:
How are the names of binary ionic compounds determined?
•A binary compound is composed of two elements and can
be either ionic or molecular.
•To name any binary ionic compound, place the cation name
first, followed by the anion name.
How do you write the formulas for binary ionic compounds?
•Write the symbol of the cation and then the anion. Add
whatever subscripts are needed to balance the charges.
Conceptual Problem 9.2
Conceptual Problem 9.2
Conceptual Problem 9.2
a) NaI
c) K2S
b) SnCl2
d) CaI2
Compounds With Polyatomic Ions
How do you write the formulas and names of
compounds containing polyatomic ions?
Write the symbol for the cation followed by the
formula for the polyatomic ion and balance the
charges.
For example, calcium nitrate is composed of a calcium
cation (Ca2+) and a polyatomic nitrate anion (NO3–).
In calcium nitrate, two nitrate anions, each with a 1–
charge, are needed to balance the 2+ charge of each
calcium cation. The formula for calcium nitrate is
Ca(NO3)2.
Conceptual Problem 9.2
Conceptual Problem 9.2
Conceptual Problem 9.2
Conceptual Problem 9.2
a) (NH4)2SO3
b) Ca3(PO4)2
Compounds With Polyatomic Ions
Naming Compounds with Polyatomic Ions
To name a compound containing a polyatomic ion, state
the cation first and then the anion, just as you did in
naming binary ionic compounds.
ex. (NH4)2SO3
ammonium sulfite
Ca3(PO4)2
calcium phosphate
Don’t change polyatomic ion names
like you would a monotomic anion!
9.2 Section Quiz
1. The correct name for CrCl3 is
a) chromium chlorine.
b) chromium(III) chloride.
c) monochromium trichloride.
d) chromium(III) trichloride.
9.2 Section Quiz
2. What is the correct formula for strontium
nitride?
a) Sr3N2
b) SrN2
c) Sr2N3
d) Sr3N
9.2 Section Quiz
3.Which one of the following compounds is
named correctly?
a) sodium chlorite, NaClO
b) potassium nitrate, KNO2
c) sodium acetate, NaC2H3O2
d) lithium sulfate, Li2SO3
9.3 Naming and Writing Formulas for
Molecular Compounds
What does a prefix in the name of a binary molecular
compound tell you about the compound’s composition?
A prefix in the name of a binary molecular
compound tells how many atoms of an element are
present in each molecule of the compound.
•9.
Naming Binary Molecular Compounds
3
Carbon and oxygen combine to form carbon monoxide
(CO) and carbon dioxide (CO2), but these two invisible
gases are very different.
Sitting in a room with small amounts of CO2 in the air
would not present any problems. If the same amount of CO
were in the room, you could die of asphyxiation. A naming
system that distinguishes between these two compounds is
needed.
Writing Formulas for Binary Molecular
Compounds
How do you write the formula for a binary molecular
compound?
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.
•9.
Naming
Binary Molecular Compounds
3
Some guidelines for naming binary molecular compounds:
– Name the elements in the order listed in the formula.
– Use prefixes to indicate the number of each kind of atom.
– Omit the prefix mono- when the formula contains only
one atom of the first element in the name.
– The suffix of the name of the second element is -ide.
Ex. Silicon carbide is a hard
material like diamond. The
name silicon carbide has no
prefixes, so the subscripts of
silicon and carbon must be one.
Thus, the formula for silicon
carbide is SiC.
9.3 Section Quiz
1. Which of the following compounds is named
INCORRECTLY?
a) CS2, carbon disulfide
b) BCl3, boron trichloride
c) IF7, iodine heptafluoride
d) PCl5, phosphorus hexachloride
9.3 Section Quiz
2. Which of the following molecular compounds
is named INCORRECTLY?
a) SbCl3, antimony trichloride
b) C2O5, dicarbon pentoxide
c) CF4, carbon tetrafluoride
d) H3As, hydrogen arsenide
9.3 Section Quiz
3. The correct formula for tetraphosphorus
trisulfide is
a) P3S4
b) S3P4
c) P4S3
d) S4P3
9.4 Naming and Writing Formulas
for Acids and Bases
Three rules can help you name an acid with
the general formula HnX.
1)
When the name of the anion (X) ends in -ide, the acid name begins
with the prefix hydro-. The stem of the anion has the suffix -ic and is
followed by the word acid.
2) 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.
3) When the anion name ends in -ate, the acid name is the stem of the
anion with the suffix -ic followed by the word acid.
An acid is a compound that contains one or more hydrogen
atoms and produces hydrogen ions (H+) when dissolved in
water. Acids have various uses.
Summary of Naming Acids
How are the formulas of acids determined?
Use the rules for writing the
names of acids in reverse to write
the formulas for acids.
What is the formula for hydrobromic
acid? Following Rule 1, hydrobromic
acid (hydro- prefix and -ic suffix)
must be a combination of hydrogen
ion (H+) and bromide ion (Br–). The
formula of hydrobromic acid is HBr.
Know these acids (except carbonic) and
the other hydro- examples
How are bases named?
Bases are named in the same way as other
ionic compounds—the name of the cation is
followed by the name of the anion.
For example, aluminum hydroxide consists of the
aluminum cation (Al3+) and the hydroxide anion
(OH–). The formula for aluminum hydroxide is
Al(OH)3.
Be able to name bases.
9.4 Section Quiz
1. The name for H2S(aq) is
a) sulfuric acid.
b) hydrosulfuric acid.
c) sulfurous acid.
d) hydrosulfurous acid.
9.4 Section Quiz
2. The correct chemical name for NH4OH is
a) nitrogen tetrahydrogen hydroxide.
b) nitrogen pentahydrogen oxide.
c) ammonium oxyhydride.
d) ammonium hydroxide.