N a 2 S O 4 ( a q ) + B a ( N O 3 ) 2 ( a q ) → B a S O 4 ( s ) + 2 N a N O 3 ( a q ) Break up the compounds into ions from which they came and cross out the ones that appear on both sides; those are your spectator ions . 2 N a + ( a q ) + S O 2 − 4 ( a q ) + B a 2 + ( a q ) + 2 N O − 3 ( a q ) → B a S O 4 ( s ) ⏐ ⏐ ↓ + 2 N a + ( a q ) + 2 N O − 3 ( a q ) Barium sulfate is insoluble so it doesn't ionize in solution Write net ionic equation S O 2 − 4 ( a q ) + B a 2 + ( a q ) → B a S O 4 ( s ) ⏐ ⏐ ↓