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 +, Cd 2+, Zn 2+, and Al 3+. These types of ions are named by using the name of the element followed by the word ion. Na + sodium ion Ba 2+ barium ion Zn 2+ 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. Cu 2+ copper (II) Pb 4+ lead (IV) Mn 7+ 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 O 2- oxide ion N 3- nitride ion Count back from the noble gases starting at zero to determine the oxidation number.

Name these monatomic ions Rb + P 3- Fe 3+ Br‾ Mn 4+ Cd 2+ 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 S 2- Pb 2+ Ba 2+ Cr 4+ Al 3+ C 4-

Atoms of elements and Ions of elements are different

Atoms of elements A pale yellow-green gas, chlorine killed soldiers in WWI. Today it mainly purifies drinking water and swimming pools. Sodium is a soft, silvery highly reactive metal. It is used in making light bulbs and for heat exchange in nuclear reactors.

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 - )