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Learn about polyatomic ions, stable groups of atoms with a net electric charge, and how to name them and write their chemical formulas. Includes common examples and exceptions.
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Stable groups of several atoms that behave together as a single charged particle. These atoms bond in such a way that they have a net electric charge (usually negative) Here are some of the most common polyatomic ions. The resulting group of atoms is an ion. So, it can form an ionic bond with a metal (most of the time for the negative charge) Polyatomic Ions You need to memorize these!!!!
We will not be drawing the structures for these atoms at this time. However, we do need to be able to name them. Write the name of the metal (including the roman numeral if necessary) 2. Write the name of the polyatomic ion Note: For a polyatomic ion, you do not need to change the ending to - ide. Name the following Ca3(PO4)2 Calcium Phosphate CuSO4 Copper (II) Sulphate BeCO3 Beryllium Carbonate Naming Compounds Involving Polyatomic Ions
There is only one really common positive polyatomic ion, This polyatomic will form ionic compounds with non metals. To name these compounds, Write the name of the polyatomic ion Write the name of the non metal changing the ending to - ide NH4+ Ammonium NH4Cl Ammonium Chloride (NH4)2O Ammonium Oxide Polyatomic Exception
Give the chemical formula for the following compounds Manganese (II) Sulphide Tin (IV) Fluoride Copper (II) Phosphate Ammonium Sulphate MnS SnF4 Cu3 (PO4)2 (NH4)2SO4 Multivalent/Polyatomic Chemical Formulae
e.g. 1/ What is the chemical formula of sodium phosphate? Step 1 – Write the symbols of each ion, beginning with the cation (metal) Na PO4 Step 2 – Write the ionic charge above each ion + 1 -3 Na PO4 Step 3 – Cross the charge to the oppose ion subscript + 1 -3 Na PO4 Step 4 – Re-write the formula. Make sure you put brackets around the polyatomic ion if it has gained a new subscript! = Na3PO4 Try: Copper (II) Nitrate