Chem – PER Versus HYPO

What does PER Versus HYPO mean in the Beginning of Polyatomic Ion Names?

Video Explanation of PER Versus HYPO in the Beginning of Polyatomic Ion Names

Group 2 of the polyatomic ion list starts introducing us to the addition of PER and HYPO. Like ATE and ITE, PER and HYPO are a continuation of the counting of oxygens. In most cases (but not all) PER adds one more oxygen from ATE. In most cases (but not all) HYPO is minus one oxygen from ITE.


Examples: Adding Per or Hypo can changed the count of the oxygens.

IO4 Periodate
IO3 Iodate
IO2 Iodite
IO Hypoiodite


PRACTICE PROBLEMS: Without looking at the polyatomic ions list try to write in how many oxygen each ion has by comparing it to its neighbor above or below. The first problem is done for you as an example.


Name Amount of Oxygen
Perchlorate 4 oxygen
Chlorate 3 oxygen
Chlorite 2 oxygen
Hypochlorite 1 oxygen
Bromite 2 oxygen
Hypobromite 1 oxygen
Perbromate 4 oxygen
Bromate 3 oxygen


Leave a Reply

You must be logged in to post a comment.