Carbon represents one of the most abundant chemical elements on Earth and by its mass, falls second only to oxygen. Life on Earth owes is existence to carbon, as it is the chemical basis for all living things on this planet. Because of its four valence electrons, carbon molecules bond with oxygen, hydrogen and nitrogen. Carbon also bonds with phosphorus and sulfur to form the biochemical building blocks that include fats, proteins and carbohydrates. Without carbon, humans would not exist in the form they do today.
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Carbon's characteristics include its ability to bond with oxygen, hydrogen, nitrogen, phosphorus and sulfur. Carbon biochemical compounds are essential to all life on the planet. Because of its bonding ability, carbon can form single, double, or triple covalent bonds with other atoms.
Multiple Physical Forms
As an allotropic biochemical element, carbon exists in multiple physical forms, even though they are chemically similar. Carbon exists as graphite, diamond or carbon residue left behind when carbon-based compounds experienced heat and pressure. Graphite, which exists in a sheet-like structure, is soft and conducts electricity. By contrast, diamond is extremely hard, does not conduct electricity and is inert. Carbon residue includes coal, charcoal and other substances that humans use for energy.
Carbon Atom Structure
A stable carbon atom possesses six protons, six neutrons and six electrons, resulting in an atomic mass of 12.011 and sits in the sixth position on the Periodic Table of Elements. Four of its electrons are found in the outer shell of the atom, while the other two exist in the inner shell. Solid-state molecules consisting of only bonded carbon atoms form tetrahedral or hexagonal shapes, depending on the physical status of the substance.
Carbon burns in oxygen to create carbon dioxide and carbon monoxide. Carbon can also form carbides when heated with oxides. For example, calcium oxide heated with carbon forms calcium carbide and carbon monoxide. In addition, carbon compounds such as carbon monoxide act as a reducing agent to metallic oxides. For example, applying extreme heat from a source such as a furnace to ferric oxide in a carbon monoxide environment reduces the ferric oxide to iron.
Carbon can form chains of carbon in single, double and triple bonds with other carbon atoms. Called catenation, this process is the basis for the creation of organic compounds and the study of organic chemistry. Although other elements such as silicon or germanium are capable of limited catenation, carbon can also form chains of unlimited size. In addition, only carbon can catenate double and triple bonds whereas other elements can only form single bonds.