chlorate polyatomic ion

FysicsPhorums

Hi, I was reviewing the polyatomic ions, and on the third row of the periodic table they seemed to follow a pattern going from left to right on the periodic table. For example:
Silicate = SiO₄^4-; phosphate = PO₄^3-; sulfate = SO₄^2-

For row 3 on the periodic table, it looks like each polyatomic has 4 oxygens, the charge increases by one as one moves to the right along the periodic table, and I think the oxidation numbers of the non-oxygen elements goes +4, +5, +6, respectively. However, chlorate is ClO₃^-, which seems to break the pattern, since it has only 3 oxygens instead of 4, and the oxidation number on chlorine of +5, instead of +7.

Is there any reason chlorate seems to "break" the pattern of the polyatomic ions so far, and any reason why for naming purposes, ClO₃^- is chlorate, instead of chlorite (like PO₃^3- is phosphite, for example)?

Thanks!

samblohm

Well actually there is a Perchlorate ion that is ClO4 that has a negative 1 charge so the pattern isn't broken. Chlorine is just very flexible in a sense because it can have anywhere between 1-4 oxygen atoms and still have a minus 1 charge.
ClO is Hypochlorite
ClO2 is Chlorite
ClO3 is Chlorate
ClO4 is Perchlorate
The naming has to do with the other form of the polyatomic ion can be.

FysicsPhorums

So is ClO₄^- called perchlorate simply because there is no ClO₅^-? I understand how perchlorate would be named relative to chlorate, and so on, but I'm trying to figure out why the naming for the other polyatomic ions I mentioned had 4 oxygens for the "ate" names. But for chlorate, the form with 3 oxygens carries the "ate" name. Thanks again for the help!

samblohm

In general, the most common oxyanion for an element will end in ate. You will find many trends in the periodic table, but you will also find many exceptions.

Some examples I can think of for ate's that have 3 oxygens are nitrate, bromate, iodate, carbonate (although that has a minus 2 charge)

And I don't think there is an element that has 5 different oxyanions.

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samblohm	Well actually there is a Perchlorate ion that is ClO4 that has a negative 1 charge so the pattern isn't broken. Chlorine is just very flexible in a sense because it can have anywhere between 1-4 oxygen atoms and still have a minus 1 charge. ClO is Hypochlorite ClO2 is Chlorite ClO3 is Chlorate ClO4 is Perchlorate The naming has to do with the other form of the polyatomic ion can be.

FysicsPhorums	So is ClO₄^- called perchlorate simply because there is no ClO₅^-? I understand how perchlorate would be named relative to chlorate, and so on, but I'm trying to figure out why the naming for the other polyatomic ions I mentioned had 4 oxygens for the "ate" names. But for chlorate, the form with 3 oxygens carries the "ate" name. Thanks again for the help!

samblohm	chlorate polyatomic ion In general, the most common oxyanion for an element will end in ate. You will find many trends in the periodic table, but you will also find many exceptions. Some examples I can think of for ate's that have 3 oxygens are nitrate, bromate, iodate, carbonate (although that has a minus 2 charge) And I don't think there is an element that has 5 different oxyanions.