Monatomic Ions
Ion Vocabulary
• An ion is an atom or group of atoms that have a
charge.
• A monatomic ion is an atom with a charge.
• The charge on the atom is called an oxidation
number.
• A polyatomic ion is a group of atoms with a
charge.
• A cation is a positive ion.
• An anion is a negative ion.
Types of monatomic ions and the
rules for naming them
• The periodic table is useful in naming the monatomic
ions.
Monatomic cations with one oxidation number
• The cations from the periodic table which have a
single oxidation number are as follows: Group 1 (+1),
Group 2 (+2), Ag+, Cd2+, Zn2+, and Al3+.
• These types of ions are named by using the name of
the element followed by the word ion.
• Na+ sodium ion
• Ba2+ barium ion
• Zn2+ zinc ion
• We can use the roman numeral from the periodic table
to identify the oxidation number for these ions.
Monatomic cations with multiple oxidation numbers
• All other cations that are not listed in the previous
category (“cations with one oxidation number”) are
considered to have the possibility of multiple oxidation
numbers.
• These type of ions are named by using the name of the
element followed by a Roman numeral to indicate the
oxidation number.
• Cu2+ copper (II)
• Pb4+ lead (IV)
• Mn7+ manganese (VII)
• It is important to note that the roman numerals in
these names may or may not be the roman numeral
from the periodic table. In other words the periodic
table is of little or no help in determining their
oxidation numbers.
Monatomic anions
• All anions from the periodic table are
named by changing the ending of the
element’s name to –ide.
• F- fluoride ion
• O2- oxide ion
• N3- nitride ion
• Count back from the noble gases starting
at zero to determine the oxidation number.
Name these monatomic ions
•
•
•
•
•
•
Rb+
P3Fe3+
Br‾
Mn4+
Cd2+
Rubidium ion
Phosphide
Iron III
Bromide
Manganese IV
Cadmium ion
Write the formula for these
monatomic ions.
•
•
•
•
•
•
Sulfide
Lead (II)
Barium ion
Chromium (IV)
Aluminum ion
Carbide
S2Pb2+
Ba2+
Cr4+
Al3+
C4-
Atoms of elements and Ions of
elements are different
Atoms of elements
Sodium is a soft, silvery highly reactive
metal. It is used in making light bulbs
and for heat exchange in nuclear
reactors.
A pale yellow-green gas, chlorine
killed soldiers in WWI. Today it
mainly purifies drinking water and
swimming pools.
Ions of elements
Combined together sodium and chlorine make common
table salt and are thus essential to life. Table salt
consists of sodium ions (Na+) and chloride ions (Cl-)