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when you take a general chemistry class you often have to memorize some of the common polyatomic ions so let's go through a list of some of the ones that you might see in your class so to start off with cation here so a positively charged ion nh4 plus is called the ammonium ion and for anions there are many anions that you should know ch3coo minus is the acetate anion see n minus is the cyanide ion Oh H minus is the hydroxide anion mno4 minus is the permanganate ion and when you get to no.3 minus vs. no2 minus look at the endings so no.3 minus is nitrate all right so we haven't we have a te suffix and 8 suffix here which means more oxygens versus the aiight suffix which means fewer oxygens so we can see that nitrate has three oxygens and nitrite has two oxygens and that ending is important because it's going to help you with some of the other polyatomic ions for example let's look at this next set here of four and let's look at crate right so chlorate has three oxygens it's clo3 -1 + chlorite has fewer oxygens it has two oxygens here CLO to CLO 2 - so we have eight meaning meaning more and I meaning fewer here what about perchlorate right so here we have chlorate but we've added on a prefix this time and the prefix per means one more oxygen so perchlorate means one more oxygen than chlorate chlorate had three oxygens right and for perchlorate we add one on and we get four so perchlorate is CL 0 4 - next let's look at hypochlorite so we talked about chlorite up here so here's chlorite and then we put a prefix hypo in front of it hypo means one fewer so if we look at chloride we had two oxygens right we take one away and now we have only one oxygen and so that must be the hypochlorite ion you could have done this for for a different in here we're dealing with chlorine alright but let's say let's say instead of clo3 - let's do br br oh three - CLO three - was chlorate here we have bromine instead of chlorine so this would be bromate all right so there's another polyatomic ion and we could do another example so instead of CLL - which is hypochlorite we could have had BR OH - which would therefore be hypo bromide alright so this would be hypo bro might alright let's look at let's look at our next set of polyatomic ions alright so let's get some space down here so we have so4 2 - is called sulfate all right so we have our eighth ending and then we have four oxygens so if we go to three oxygens so3 two - this is sulfite right because I each means fewer oxygens what about if we if we took sulfate so4 2 - and we add it on an H+ alright so h+ + so4 2 - should give us hso4 and then instead of a negative 2 here instead of a 2 - we would just have a 1 - because we added on a positive charge alright so one positive charge and 2 negative charges give us one negative charge so hso4 minus is called the hydrogen sulfate ion alright you might also hear by sulfates for this one next Co 3 - - is called carbonate so if we add on an H + 2 Co 3 2 - we'd get hco3 and we go from minus 2 or 2 - 2 - 1 because we're adding on a positive charge here so hco3 - is called hydrogen carbonate and you'll also hear bicarbonate a lot next we have po4 3 - which is called phosphate if we add on an h+ - phosphate alright think about what we would get we would get hpo4 and then stead of 3 - right we're adding on a positive charge so we get 2 - so we call this hydrogen phosphate alright let's add on a proton to hydrogen phosphates we're adding an H+ onto hydrogen phosphate that would give us two H's alright po4 and we go from two - down to one - so h2 po4 - is called dihydrogen phosphate alright let's let's continue on one more set of polyatomic ions - no so we have cro4 - - which is called chromate and if we have two chromium's so cr2 o7 - - this is called dichromate next C - oh for two - is called the oxalate ion and we have o to two - is called peroxide and here we have s CN - which we call thiocyanate so thio think about sulfur if you if you see thio there so for our next one right we have sulfur present again it's s 2 O 3 2 - and this one's called thiosulfate so you might see you might see a few additional polyatomic ions in your class but these are the ones that that you see most frequently so make sure to memorize your polyatomic ions