Information AboutOxide |
| CATEGORIES ABOUT OXIDE | |
| oxides | |
|
MOST OXIDES ARE INSOLUBLE IN WATER The oxide Ion , O2−, is the Conjugate Base of the Hydroxide ion, OH−, and is encountered in Ionic solid such as Calcium Oxide . O2− is unstable in Aqueous Solution − its affinity for H+ is so great (pKb ~ -22) that it abstracts a Proton from a solvent H2O molecule: :O2− + H2O → 2 OH− Although many dissolve readily in water to give a solution containing the constituent ions, Na+ and Cl-. Oxides do not behave like this. If an iodic oxide dissolves, the O2− ions become protonated. Although Calcium Oxide , CaO, is said to "dissolve" in water, the products include Hydroxide : :CaO + H2O → Ca2+ + 2 OH- In fact, no monoatomic dianion is known to dissolve in water - all are so basic that they undergo Hydrolysis . Concentrations of oxide ion in water are too low to be detectable with current technology. Authentic soluble oxides do exist of course, but they release Oxyanion s, not O2-. Well known soluble salts of oxyanions include Sodium Sulfate (Na2SO4), Potassium Permanganate (KMnO4), and sodium nitrate (NaNO3). NOMENCLATURE In the 18th Century , oxides were named calxes or '''calces''' after the Calcination process used to produce oxides. ''Calx'' was later replaced by ''oxyd''. Oxides are usually named after the number of oxygen atoms in the oxide. Oxides containing only one oxygen are called oxides or Monoxides , those containing two oxygen atoms are Dioxides , three oxygen atoms makes it a Trioxide , four oxygen atoms are Tetroxides , and so on following the Greek Numerical Prefix es. Two other types of oxide are Peroxide , O22−, and Superoxide , O2−. In such species, oxygen is assigned higher Oxidation State s than oxide. TYPES OF OXIDES Oxides of more Electropositive elements tend to be basic. They are called basic anhydrides; adding water, they may form basic Hydroxide s. For example, Sodium Oxide is basic; when hydrated, it forms Sodium Hydroxide . Oxides of more Electronegative elements tend to be acidic. They are called acid anhydrides; adding water, they form Oxoacid s. For example, Dichlorine Heptoxide is acid; Perchloric Acid is a more hydrated form. Some oxides can act as both acid and base, at different times. They are Amphoteric . An example is Aluminium Oxide . Some oxides do not show behavior as either acid or base. The oxides of the Chemical Element s in their highest Oxidation State are predictable and the Chemical Formula can be derived from the number of Valence Electron s for that element. Even the chemical formula of Ozone is predictable as a Group 16 Element . One exception is Copper for which the highest oxidation state oxide is Copper(II) Oxide and not Copper(I) Oxide . Another exception is Fluoride that does not exist as expected as F2O7 but as OF2 with the least Electronegative element given priority. ''Fully Exploiting the Potential of the Periodic Table through Pattern Recognition'' Schultz, Emeric. J. Chem. Educ. 2005 82 1649.. Phosphorus Pentoxide , the third exception is not properly represented by the chemical formula P 2 O 5 but by P 4 O 10 COMMON OXIDES SORTED BY OXIDATION STATE
SEE ALSO
REFERENCES |
|
|