Polyatomic Ions

1. What are POLYATOMIC IONS?

2. What are POLYATOMIC IONS?
What is a group of atoms with charge?
back to
naming
compounds
Lets first review what a monatomic ion is

3. In a single atom (monatomic), charge results
from having either more electrons
or less electrons than protons.
+
+
+
+
+
Less electrons than protons
= positive charge (cations)
More electrons than protons
= negative charge (anions)
+
+
+
+
+

4. Example: The magnesium ion has
two
less electrons than protons
Mg
2+

5. Example: The magnesium ion has
two
less electrons than protons
Mg
2+ back to
polyatomic
ions

6. N
O
O
O

7. N
O
O
O
In a polyatomic ion,
two or more atoms covalently bonded together.

8. Together, they carry a charge
N
O
O
O
1–

9. The nitrate ion
(NO3
–
) has, in total,
one more electron
than protons
N
O
O
O
1–

10. When balancing charges in an ionic compound,
the polyatomic ion acts as a single unit of charge:
Mg(NO
3
)
2
Mg
2+
N
O
O
O
1-
N
O
O
O
1-

11. N
O
O
O
Mg
N
O
O
O
2+ 1-1-
2+
Mg(NO
3
)
2

12. N
O
O
O
Mg
N
O
O
O
2+ 1-1-
2+2-the charges are balanced
Mg(NO
3
)
2