What are POLYATOMIC IONS?

What is a group of atoms with charge? back to naming compounds Lets first review what a monatomic ion is

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)

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

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

N O O O

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

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

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

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-

N O O O Mg N O O O Mg(NO 3 ) 2

N O O O Mg N O O O the charges are balanced Mg(NO 3 ) 2

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