Why is (H2O2) known as hydrogen peroxide and not hydrogen dioxide?

Question

For example the gas CO known as carbon monoxide and CO2 known as carbon dioxide.

Water (H2O) is also called dihydrogen monoxide. So why isn't H2O2 known as hydrogen dioxide?

Roger the Mole · Answer

Because "hydrogen dioxide" would have to be H4O2 -- which does not exist.

Mike A · Answer

The name "dihydrogen monoxide" is only used by people with a limited knowledge of chemistry who attempt to confuse the reader by using an unfamiliar name for water. Hydrogen sulfide is the accepted name of H2S not dihydrogen monosulfide which would be pedantic and downright wrong. By analogy water would be hydrogen oxide but in practice the name water is so well established that no attempt is made to change it. In the IUPAC system of nomenclature the prefixes mono, di, tri, etc are only used when necessary to define the chemical composition of a substance so CaO is calcium oxide, Na2O is sodium oxide and MgCl2 is magnesium chloride. Not a mono or di in sight,

Dr W · Answer

the "per" is related to the charge on the oxygen component
.. peroxide... O2(2-).. each O is -1
.. superoxide.. O2(1-).. each O averages -1/2
.. oxygen... .. . .O2(0)
.. dioxygenyl.... O2(+1)
.. oxide.. . . .. .O(-2)
etc

if you start with a peroxide species and add hydrogen to get a neutral compound, you get the non-ambiguous H2O2.  Hence the name, hydrogen peroxide.

az_lender · Answer

The "per" as in "perfect" means the hydrogen is thoroughly oxidized.  As another responder said, you could call the same compound dihydrogen dioxide and everyone would figure out what you mean by that.

busterwasmycat · Answer

The idea of peroxide is that the O2 is acting as an anion ( O2(2-) ) rather than two individual ions. By saying peroxide, we define the O2 as a group entity in behavior and function, rather than as two separate atoms of O; it is not two O(2-), but one O2(2-). It is somewhat like saying carbonate when we discuss the CO3(2-2) anion. You cannot take out the separate atoms and expect the same behavior. the atoms themselves, when together, are different from the atoms themselves when apart.

Nomenclature is intended to tell us of the chemistry of the constituents. Thus, we call it peroxide to declare the chemistry. It is not a dioxide, it is a peroxide.

Nomenclature is intended to tell us of the chemistry of the constituents.  Thus, we call it peroxide to declare the chemistry.  It is not a dioxide, it is a peroxide.

K · Answer

it is also known as dihydrogen dioxide, not hydrogen dioxide

but hydrogen peroxide is the accepted norm

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Why is (H2O2) known as hydrogen peroxide and not hydrogen dioxide?

6 Answers