Oxygen, trivalent

Protonation of an oxygen link, thus leading to trivalent oxygen (first and second lines of the diagram). 

Once reaction (1) has taken place, collision of the oxygen of an ambient normal THF molecule with one of the positively charged carbon atoms leads to a reaction characterized by the fact that a new bond is formed with the positively charged carbon atom while the latter abandons one of its original bonds. In the case considered, the bond abandoned turns out to be the bond to the original trivalent oxygen, since this is the weakest of all the bonds around. The C-H bonds are very much stronger than C-C and C-0 bonds, and the C-0 bond partially depleted of electrons is weaker than the C-C bond. 

The reaction of acetic anhydride with a growing PTHF chain leads to the attachment of an acetate end group on the existing chain, and to a new chain embryo consisting of an acetate starter group bonded to a THF molecule by trivalent oxygen. This reaction is shovra below, where for the sake of clarity the hydrogen atoms bonded to the carbon atoms are now omitted. 

Oxonium ion A trivalent oxygen cation with a full octet of electrons (e.g., HsO ). Paraffins An older name for alkanes. 

The predictable number of bonds usually formed by an atom of an element is its valence. Carbon is generally tetravalent, nitrogen trivalent, oxygen divalent, and hydrogen and the halogens monovalent. 

The usual valence of indium is three, although monovalent and bivalent compounds of indium with oxygen, halogens, and Group 15 (VA) and 16 (VIA) elements ate well known. The lower valence compounds tend to disproportionate into the trivalent compound and indium metal the trivalent compounds ate stable. 

Chemical Properties. Although the chemical properties of the trivalent lanthanides are quite similar, some differences occur as a consequence of the lanthanide contraction (see Table 3). The chemical properties of yttrium are very similar too, on account of its external electronic stmcture and ionic radius. Yttrium and the lanthanides are typical hard acids, and bind preferably with hard bases such as oxygen-based ligands. Nevertheless they also bind with soft bases, typicaUy sulfur and nitrogen-based ligands in the absence of hard base ligands. 

In the presence of oxygen (air), the thermal decomposition of amphiboles is associated with an oxidation of divalent iron to trivalent iron, which may lead to an increase in the sample weight the oxidation process also induces an obvious color alteration, the fibers acquire the characteristic ferric oxide... 

Sohd solutions of ceria with trivalent ions, eg, Y and La, can readily be formed. The ions substitute for the tetravalent Ce and introduce one oxygen vacancy for every two ions. The dopant ions and the oxygen vacancies form charge associates. The resulting defect-fluorites have good oxide... 

Stereoelectronic factors are also important in determining the stmcture and reactivity of complexes. Complexes of catbonyl groups with trivalent boron and aluminum compounds tend to adopt a geometry consistent with directional interaction with one of the oxygen lone pairs. Thus the C—O—M bond angle tends to be in the trigonal (120-140°) range, and the boron or aluminum is usually close to die carbonyl plane. ... 

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