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An oxide (/ ˈ ɒ k s aɪ d /) is a chemical compound containing at least one oxygen atom and one other element [1] in its chemical formula. "Oxide" itself is the dianion (anion bearing a net charge of –2) of oxygen, an O 2– ion with oxygen in the oxidation state of −2. Most of the Earth's crust consists of oxides. Even materials ...
Curves in the Ellingham diagrams for the formation of metallic oxides are basically straight lines with a positive slope. The slope is proportional to ΔS, which is approximately constant with temperature. The lower the position of a metal's line in the Ellingham diagram, the greater is the stability of its oxide.
The −1 occurs because each carbon is bonded to one hydrogen atom (a less electronegative element), and the − 1 / 5 because the total ionic charge of −1 is divided among five equivalent carbons. Again this can be described as a resonance hybrid of five equivalent structures, each having four carbons with oxidation state −1 and ...
This table lists only the occurrences in compounds and complexes, not pure elements in their standard state or allotropes. Noble gas +1 Bold values are main oxidation states
Compounds containing oxygen in other oxidation states are very uncommon: − 1 ⁄ 2 (superoxides), − 1 ⁄ 3 , 0 (elemental, hypofluorous acid), + 1 ⁄ 2 , +1 (dioxygen difluoride), and +2 (oxygen difluoride). Oxygen is reactive and will form oxides with all other elements except the noble gases helium, neon, argon and krypton. [1]
Many oxyanions of elements in lower oxidation state obey the octet rule and this can be used to rationalize the formulae adopted. For example, chlorine(V) has two valence electrons so it can accommodate three electron pairs from bonds with oxide ions. The charge on the ion is +5 − 3 × 2 = −1, and so the formula is ClO − 3.
A sesquioxide is an oxide of an element (or radical), where the ratio between the number of atoms of that element and the number of atoms of oxygen is 2:3. For example, aluminium oxide Al 2 O 3 and phosphorus(III) oxide P 4 O 6 are sesquioxides.
When the electropositive element is a metal, the compounds are sometimes referred to as “metal-rich”. Thus the normal oxide of caesium is Cs 2 O, which is described as a Cs + salt of O 2− . A suboxide of caesium is Cs 11 O 3 , where the charge on Cs is clearly less than 1+, but the oxide is still described as O 2− .