Supplement An organism refers to any individual living thing that can react to stimuli, reproduce, grow, and maintain homeostasis.
The three-domain system of biological classification as proposed by Carl Woese and others (in 1977) classifies organisms into the following domains: archaea (archaeabacteria), bacteria (eubacteria), and eucarya (eukaryotes). Organisms may also be grouped based on their cellular composition.
A single-celled organism is one that consists of only one cell.
In contrast, a multicellular organism is one that is comprised of more than one cell and whose cells are organized into tissues, organs, and then into systems.
"coal") is a chemical element with symbol C and atomic number 6.
In general, covalent radius decreases with lower coordination number and higher bond order.
Carbon compounds form the basis of all known life on Earth, and the carbon-nitrogen cycle provides some of the energy produced by the Sun and other stars.
This exothermic reaction is used in the iron and steel industry to smelt iron and to control the carbon content of steel: Carbon combines with some metals at high temperatures to form metallic carbides, such as the iron carbide cementite in steel, and tungsten carbide, widely used as an abrasive and for making hard tips for cutting tools.
The system of carbon allotropes spans a range of extremes: Atomic carbon is a very short-lived species and, therefore, carbon is stabilized in various multi-atomic structures with different molecular configurations called allotropes.
The electronegativity of carbon is 2.5, significantly higher than the heavier group 14 elements (1.8–1.9), but close to most of the nearby nonmetals as well as some of the second- and third-row transition metals.
Carbon's covalent radii are normally taken as 77.2 pm (C–C), 66.7 pm (C=C) and 60.3 pm (C≡C), although these may vary depending on coordination number and what the carbon is bonded to.
Graphite is soft enough to form a streak on paper (hence its name, from the Greek verb "γράφειν" which means "to write"), while diamond is the hardest naturally occurring material known.