Carbon

**1. Characteristics and Properties of Carbon:**
– Carbon is nonmetallic, tetravalent, and the 15th most abundant element in Earth’s crust.
– It makes up about 0.025% of Earth’s crust and is the second most abundant element in the human body by mass.
– Carbon has three naturally occurring isotopes and forms diverse allotropes like graphite, diamond, and fullerenes.
– Graphite is opaque and a good electrical conductor, while diamond is transparent and the hardest naturally occurring material.
– Carbon has high sublimation point, resists oxidation, and combines with metals to form metallic carbides.

**2. Industrial Applications and Allotropes:**
– Carbon is a component of the majority of chemical compounds and has around two hundred million described compounds.
– Allotropes of carbon include graphite, diamond, fullerenes, graphene, glassy carbon, and more.
– Graphite is used for thermal insulation and lubrication, while synthetic nanocrystalline diamond is used as an abrasive.
– Tungsten carbide is widely used for cutting tools, showcasing the diverse industrial applications of carbon.

**3. Occurrence and Distribution of Carbon:**
– Carbon is the 4th most abundant element in the observable universe and is found in the Sun, stars, comets, and planet atmospheres.
– Carbon occurs in Earth’s core, mantle, crust, atmosphere, water bodies, and biosphere.
– Hydrocarbons like coal, petroleum, and natural gas contain carbon, while graphite and natural diamonds have specific geological formations.
– Industrial diamonds are partly manufactured and used in the U.S., highlighting the global distribution of carbon resources.

**4. Reactivity and Applications of Carbon Allotropes:**
– Different forms of carbon exhibit unique reactivity, such as the glowing of diatomic carbon in vapor phase and the properties of buckyballs, nanobuds, and linear acetylenic carbon.
– Carbon allotropes like graphene, fullerenes, carbon nanofoam, and Q-carbon have diverse applications in space technology, nanomaterials, and nanotechnology.
– Q-carbon, for example, exhibits ferromagnetism, fluorescence, and superior hardness compared to diamonds, showcasing the potential of carbon in advanced applications.

**5. Isotopes, Formation in Stars, Carbon Cycle, and Emissions:**
– Carbon has two stable isotopes, carbon-12 and carbon-13, along with the radioisotope carbon-14 used in radiocarbon dating.
– Carbon nucleus formation in stars occurs through the triple-alpha process, and carbon is a component material for the formation of star systems.
– The carbon cycle involves the movement of carbon between reservoirs on Earth and is a catalyst in star processes like the CNO cycle.
– Carbon emissions from burning fossil fuels have released gigatonnes of carbon into the atmosphere, impacting the environment and prompting considerations for space-based carbon mining.