Ask A Scientist© Chemistry Archive

name         Abby C.
status       student
age          14

Question -   How, when ,why are is the root change in naming different
elemnts in a formula.   For the second element in a binary you are to ad
"ide", explain how, when, why is "ite" and "ate" added to the root?
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These are some accidents of history, which if it were possible, most
chemists would like to retract, because when the suffixes were applied to
various substances the chemistry in many cases was not well understood. But
we are stuck with them so here goes:
-ide usually means that the element is in its elemental anionic form. So we
have chloride, bromide, ... , oxide, sulfide,..., nitride, phosphide... And
there are no oxygens attached to the "-ide" element.

-ate usually means the element in to which the largest possible number of
oxygen atoms are attached. So we have chlorate [ClO3^-1], sulfate, phosphate
and so on. However, some elements were found that contained more oxygens
than was first thought possible so the naming system had to be patched up
the take into account. So we have PER-chlorate [ClO4^-1].

-ite refers to the oxygenated anion of an element that contains some
intermediate number of oxygen atoms. So we have sulfite [SO3^-2] and
chlorite [ClO2^-1], but then comes along [ClO^-1]. What to do? Invent a new
prefix, so we get HYPOchlorite.

There are of course the corresponding -ic, and -ous acids, too!!

Vince Calder
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The only hard and fast rule is that "ate" is a higher oxidation state than
"ite," which is a higher oxidation state than "ide."  Sometimes you need
additional prefizes to fill the whole spectrum.  The classic example is the
halogens, take for instance chlorine.

   Cl-     chloride
   ClO-    hypochlorite
   ClO2-   chlorite
   ClO3-   chlorate
   ClO4-   perchlorate

Richard E. Barrans Jr., Ph.D.
Assistant Director
PG Research Foundation, Darien, Illinois
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