Polyatomic Ions SNC2D

P OLYATOMIC I ONS ● Polyatomic ions are groups of atoms that tend to stay together and carry an overall ionic charge ● The ion is typically held together with covalent bonds ● The polyatomic ion is capable of bonding with other ions

P OLYATOMIC I ONS TO K NOW ● Below is the list of polyatomic ions you need know ● The list is from the periodic table for SNC2DI

W RITING F ORMULAS WITH P OLYATOMIC I ONS 1.Write the symbol for the cation first and the anion second 1.Write the combining capacity for each element over each of the ions (for polyatomic ions this is the same as the ionic charge) 1.Use “cross over” method and reduce numbers to lowest ratio without changing the formula for the ion Na + SO 4 2- → Na 2 SO 4 Al + OH - → Al(OH) 3 NH NO 3 - → NH 4 NO 3

N AMING C OMPOUNDS C ONTAINING P OLYATOMIC I ONS ● Name of the metal first ● Name of the polyatomic ion second ● Polyatomic ions usually end in “ate” Na 2 SO 4 → sodium sulphate Al(OH) 3 → aluminum hydroxide NH 4 NO 3 → ammonium nitrate

O XYACIDS ● When hydrogen bonds to many of the polyatomic ions that contain oxygen, oxyacids form: ● nitrate (NO 3 - ) → nitric acid (HNO 3 ) ● phosphate (PO 4 3- ) → phosphoric acid (H 3 PO 4 )