Grade 10 Academic Science – Chemistry
Polyatomic Ion
Science Perspectives 10 – Section 5.9 Pages 202-205
A polyatomic ion is a charged ion composed of two or more atoms COVALENTLY BONDED
acting as a single unit.
 The prefix "poly-" means "many," in Greek. Thus, two covalently bonded atoms are
referred to as polyatomic.
From your textbook, a polyatomic ion is an ion that consists of a stable group of several atoms
acting together as a single charged particle.
Table 1. Formula and Charges of Common Polyatomic Ions
Name of Polyatomic Ion
Ionic Formula
Ionic
Charge
Suffix
Nitrate ion
NO3-
-1
ate
Nitrite ion
NO2-
-1
ite
Hydroxide ion
OH-
-1
ide
Hydrogen carbonate ion
HCO3-
-1
ate
Chlorate ion
ClO3-
-1
ate
Carbonate ion
CO32-
-2
ate
Sulfate ion
SO42-
-2
ate
Phosphate ion
PO43-
-3
ate
Ammonium
NH4+
+1
NOTE: The chare of a polyatomic ion is shared over the ENTIRE ION.
NOTE: Hydrogen carbonate ion is also BICARBONATE ion. When the prefix “bi” is added to a
name, it means a hydrogen has bonded with the ion.
A two-dimensional drawing of the bicarbonate ion is shown opposite.
From the illustration, can you explain WHY the bicarbonate ion has a
single charge of -1? NOTE: Each line represents a bond of two
electrons while a dot represents one electron. This is the basis for
understanding polyatomic bonding, although the rules as we know
them may not always apply – good start.
TASK
 Read Pages 202-205 in your textbook to learn about naming and writing formula for
polyatomic ions.
 Complete Questions 1-12