Health

No smoking four weeks before operation cuts risks: WHO

Patients who stop smoking at least four weeks before an operation significantly reduce the risk of having postsurgical complications because their blood flow improves, according to a study published Monday.

Health

Is sparkling water bad for you?

For many people, the start of a year is a time for new health resolutions—be it eat more vegetables, consume less sugar or drink more water.

Medical research

Saccharin derivatives give cancer cells a not-so-sweet surprise

Saccharin received a bad rap after studies in the 1970s linked consumption of large amounts of the artificial sweetener to bladder cancer in laboratory rats. Later, research revealed that these findings were not relevant ...

Radiology & Imaging

Imaging uncovers secrets of medicine's mysterious ivory manikins

Little is known about the origins of manikins—small anatomical sculptures thought to be used by doctors four centuries ago—but now advanced imaging techniques have offered a revealing glimpse inside these captivating ...

Health

Risk for carbon monoxide poisoning increases in winter

Each year, carbon monoxide (CO) poisoning is responsible for more than 50,000 emergency department visits, resulting in more than 400 deaths according to the Centers for Disease Control and Prevention. Americans ages 65 ...

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Carbon

Carbon (pronounced /ˈkɑrbən/) is the chemical element with symbol C and atomic number 6. As a member of group 14 on the periodic table, it is nonmetallic and tetravalent—making four electrons available to form covalent chemical bonds. There are three naturally occurring isotopes, with 12C and 13C being stable, while 14C is radioactive, decaying with a half-life of about 5730 years. Carbon is one of the few elements known since antiquity. The name "carbon" comes from Latin language carbo, coal, and, in some Romance and Slavic languages, the word carbon can refer both to the element and to coal.

There are several allotropes of carbon of which the best known are graphite, diamond, and amorphous carbon. The physical properties of carbon vary widely with the allotropic form. For example, diamond is highly transparent, while graphite is opaque and black. Diamond is among the hardest materials known, while graphite is soft enough to form a streak on paper (hence its name, from the Greek word "to write"). Diamond has a very low electrical conductivity, while graphite is a very good conductor. Under normal conditions, diamond has the highest thermal conductivity of all known materials. All the allotropic forms are solids under normal conditions but graphite is the most thermodynamically stable.

All forms of carbon are highly stable, requiring high temperature to react even with oxygen. The most common oxidation state of carbon in inorganic compounds is +4, while +2 is found in carbon monoxide and other transition metal carbonyl complexes. The largest sources of inorganic carbon are limestones, dolomites and carbon dioxide, but significant quantities occur in organic deposits of coal, peat, oil and methane clathrates. Carbon forms more compounds than any other element, with almost ten million pure organic compounds described to date, which in turn are a tiny fraction of such compounds that are theoretically possible under standard conditions.

Carbon is one of the least abundant elements in the Earth's crust, but the fourth most abundant element in the universe by mass after hydrogen, helium, and oxygen. It is present in all known lifeforms, and in the human body carbon is the second most abundant element by mass (about 18.5%) after oxygen. This abundance, together with the unique diversity of organic compounds and their unusual polymer-forming ability at the temperatures commonly encountered on Earth, make this element the chemical basis of all known life.

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