Medical research

New research shows how stress can weaken defenses

Research from the lab of Mark Alkema, Ph.D., professor of neurobiology, sheds light on how the "flight-or-flight" response impairs long-term organism health. The study, conducted in the nematode worm, C. elegans, a common ...

Health

Scientists find thirdhand smoke affects cells in humans

Thirdhand smoke can damage epithelial cells in the respiratory system by stressing cells and causing them to fight for survival, a research team led by scientists at the University of California, Riverside, has found. The ...

Medical research

New basic understanding of how lung cancer spreads

Lung cancer cells use antioxidants, endogenous or dietary, to spread in the body by activating a protein called BACH1 and increasing the uptake and use of sugar, Swedish and American researchers report in two independent ...

Oncology & Cancer

Too many antioxidants may cause lung cancer spread

A new study explains why lung cancer spreads faster in patients with certain genetic changes, and suggests that taking vitamin E, long thought of as preventive, may cause the same spread.

Medical research

Study finds direct oxidative stress damage shortens telomeres

The same sources thought to inflict oxidative stress on cells—pollution, diesel exhaust, smoking and obesity—also are associated with shorter telomeres, the protective tips on the ends of the chromosomal shoelace.

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Oxide

An oxide ( /ˈɒksaɪd/) is a chemical compound that contains at least one oxygen atom in its chemical formula. Metal oxides typically contain an anion of oxygen in the oxidation state of −2.

Most of the Earth's crust consists of solid oxides. Oxides result when elements are oxidized by oxygen in air. Combustion of hydrocarbons affords the two principal oxides of carbon, carbon monoxide and carbon dioxide. Even materials that are considered to be pure elements often contain a coating of oxides. For example, aluminium foil has a thin skin of Al2O3 that protects the foil from further corrosion.

Virtually all elements burn in an atmosphere of oxygen, or an oxygen rich environment. In the presence of water and oxygen (or simply air), some elements—lithium, sodium, potassium, rubidium, caesium, strontium and barium—react rapidly, even dangerously, to give the hydroxides. In part for this reason, alkali and alkaline earth metals are not found in nature in their metallic, i.e., native, form. Caesium is so reactive with oxygen that it is used as a getter in vacuum tubes, and solutions of potassium and sodium, so called NaK are used to deoxygenate and dehydrate some organic solvents. The surface of most metals consists of oxides and hydroxides in the presence of air. A well known example is aluminium foil, which is coated with a thin film of aluminium oxide that passivates the metal, slowing further corrosion. The aluminium oxide layer can be built to greater thickness by the process of electrolytic anodising. Although solid magnesium and aluminium react slowly with oxygen at STP, they, like most metals, will burn in air, generating very high temperatures. Finely grained powders of most metals can be dangerously explosive in air. Consequently, they are often used in Solid-fuel rockets.

In dry oxygen, iron readily forms iron(II) oxide, but the formation of the hydrated ferric oxides, Fe2O3−2x(OH)x, that mainly comprise rust, typically requires oxygen and water. The production of free oxygen by photosynthetic bacteria some 3.5 billion years ago precipitated iron out of solution in the oceans as Fe2O3 in the economically important iron ore hematite.

Due to its electronegativity, oxygen forms chemical bonds with almost all elements to give the corresponding oxides. Noble metals (such as gold or platinum) resist direct chemical combination with oxygen, and substances like gold(III) oxide must be generated by indirect routes.

This text uses material from Wikipedia, licensed under CC BY-SA