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 2+ Mg

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

6. N O O O

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

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

9. The nitrate ion (NO 3 – ) 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. 2+ 1 - 1 - 2+ Mg(NO 3 ) 2 N O O O Mg N O O O

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