A sesquioxide is an oxide of an element (or radical), where the ratio between the number of

atoms Every atom is composed of a nucleus and one or more electrons bound to the nucleus. The nucleus is made of one or more protons and a number of neutrons. Only the most common variety of hydrogen has no neutrons. Every solid, liquid, gas ...

of that element and the number of atoms of

oxygen Oxygen is the chemical element with the symbol O and atomic number 8. It is a member of the chalcogen group in the periodic table, a highly reactive nonmetal, and an oxidizing agent that readily forms oxides with most elements as we ...

is 2:3. For example, aluminium oxide and phosphorus(III) oxide are sesquioxides. Many sesquioxides contain a

metal A metal (from Greek μέταλλον ''métallon'', "mine, quarry, metal") is a material that, when freshly prepared, polished, or fractured, shows a lustrous appearance, and conducts electricity and heat relatively well. Metals are typi ...

in the +3

oxidation state In chemistry, the oxidation state, or oxidation number, is the hypothetical charge of an atom if all of its bonds to different atoms were fully ionic. It describes the degree of oxidation (loss of electrons) of an atom in a chemical compound. ...

and the oxide ion , e.g., aluminium oxide , lanthanum(III) oxide and

iron(III) oxide Iron(III) oxide or ferric oxide is the inorganic compound with the formula Fe2O3. It is one of the three main oxides of iron, the other two being iron(II) oxide (FeO), which is rare; and iron(II,III) oxide (Fe3O4), which also occurs naturally ...

. Sesquioxides of

iron Iron () is a chemical element with symbol Fe (from la, ferrum) and atomic number 26. It is a metal that belongs to the first transition series and group 8 of the periodic table. It is, by mass, the most common element on Earth, right in ...

and

aluminium Aluminium (aluminum in AmE, American and CanE, Canadian English) is a chemical element with the Symbol (chemistry), symbol Al and atomic number 13. Aluminium has a density lower than those of other common metals, at approximately o ...

are found in

soil Soil, also commonly referred to as earth or dirt, is a mixture of organic matter, minerals, gases, liquids, and organisms that together support life. Some scientific definitions distinguish ''dirt'' from ''soil'' by restricting the former ...

. The alkali metal sesquioxides are exceptions because they contain both

peroxide In chemistry, peroxides are a group of compounds with the structure , where R = any element. The group in a peroxide is called the peroxide group or peroxo group. The nomenclature is somewhat variable. The most common peroxide is hydrogen ...

and

superoxide In chemistry, a superoxide is a compound that contains the superoxide ion, which has the chemical formula . The systematic name of the anion is dioxide(1−). The reactive oxygen ion superoxide is particularly important as the product of ...

ions, e.g., rubidium sesquioxide is formulated . Sesquioxides of metalloids and nonmetals are exceptions too, e.g. boron trioxide , dinitrogen trioxide and phosphorus(III) oxide . Many

transition metal In chemistry, a transition metal (or transition element) is a chemical element in the d-block of the periodic table (groups 3 to 12), though the elements of group 12 (and less often group 3) are sometimes excluded. They are the elements that c ...

oxides crystallize in the

corundum Corundum is a crystalline form of aluminium oxide () typically containing traces of iron, titanium, vanadium and chromium. It is a rock-forming mineral. It is a naturally transparent material, but can have different colors depending on the ...

structure type, with

space group In mathematics, physics and chemistry, a space group is the symmetry group of an object in space, usually in three dimensions. The elements of a space group (its symmetry operations) are the rigid transformations of an object that leave it ...

Rc. Sesquioxides of rare earth elements crystalize into one or more of three crystal structures: hexagonal (type A, space group Pm1), monoclinic (type B, space group C2/m), or body-centered cubic (type C, space group Ia). Sesquioxidizing, meaning the creation of a sesquioxide, is the highest scoring word that would fit on a

Scrabble ''Scrabble'' is a word game in which two to four players score points by placing tiles, each bearing a single letter, onto a game board divided into a 15×15 grid of squares. The tiles must form words that, in crossword fashion, read left ...

board, though it does not actually appear in any official Scrabble dictionary. Though the

Oxford English Dictionary The ''Oxford English Dictionary'' (''OED'') is the first and foundational historical dictionary of the English language, published by Oxford University Press (OUP). It traces the historical development of the English language, providing a com ...

already listed the noun and the past participle adjective — sesquioxidation and sesquioxidized, respectively — the verb, sesquioxidize, and its conjugated forms, have been absent from the dictionaries used as sources for the official Scrabble word lists. An early appearance of the noted present participle had occurred in the 1860 publication of the State of New York's Legislative Assembly's Transactions of the State Medical Society, yet the word's first appearance in a dictionary was in the 1976 edition of Josepha Heifetz Byrne's ''Mrs. Byrne's Dictionary of Unusual, Obscure, and Preposterous Words'' (), One could theoretically score 2044 points in a single move, when otherwise only words from the official Scrabble word list are used.Record for the Highest Scoring Scrabble Move
at scrabulizer.com, accessed 2008-05-30

List of sesquioxides

References

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