1. What are POLYATOMIC IONS?

2. 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 1–1–

9. The nitrate ion (NO 3 – ) has, in total, one more electron than protons N O O O 1–1–

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 1-1- N O O O 1-1-

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

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

13. back to first slide back to naming compounds previous slide