Carbon

Diamond and graphite are carbon allotropes: they are made of the same element, but their atoms are arranged differently. In diamond, each atom is joined to four neighbours in a very rigid three-dimensional network, giving extreme hardness and electrical insulation. In graphite, atoms form layers that can slide, so it is soft, lubricating and conductive. Structure, not just composition, determines their properties.

Carbon is neither good nor bad by itself: it is the basis of life and forms part of CO₂, fossil fuels and all living organisms. The environmental problem arises when large amounts of carbon stored for millions of years are released through oil, coal or natural gas, increasing greenhouse gases. The natural carbon cycle includes photosynthesis, respiration and decomposition; human activity has altered its balance.

Yes. Graphite conducts electricity because its electrons can move relatively easily within its layers of carbon atoms. This property, together with its thermal stability, makes it useful in electrodes, batteries, motor brushes and electrical components. Diamond, on the other hand, is an electrical insulator under normal conditions because its electrons are strongly bonded in a three-dimensional network. Both are pure carbon, but their atomic arrangement produces opposite electrical behaviours.

In theory, graphite can be transformed into diamond, but it requires very high pressure and temperature conditions, similar to those of the Earth's interior, or controlled industrial processes. It does not occur spontaneously at room temperature because the transformation needs to overcome a significant energy barrier. There are synthesis methods of diamond, such as high pressure and high temperature or chemical vapour deposition, that produce diamonds for industrial tools, optics and, in some cases, jewellery.

The carbon footprint is the total amount of greenhouse gases emitted directly or indirectly by a person, company, product or activity, usually expressed in tonnes of carbon dioxide equivalent. It includes, for example, energy consumption, transport, manufacturing of goods and waste management. Reducing it implies improving energy efficiency, using cleaner transport, consuming more responsibly and resorting to renewable energies. It should not be confused with the element carbon itself.

Activated charcoal is a form of carbon with an extremely porous internal surface, capable of adsorbing molecules. It is used in water and air filters, masks, purification systems, effluent treatment and some pharmaceuticals. Its effectiveness depends on the type of contaminant, contact time and filter design. It does not remove all contaminants equally and must be replaced periodically, as once saturated it loses its retention capacity.

Graphene is a single layer of carbon atoms arranged in a two-dimensional hexagonal network; graphite is formed by many of these layers stacked. That is why graphene is extremely thin, light, flexible and an excellent electrical and thermal conductor. It is investigated for screens, batteries, sensors, composite materials and advanced electronics. Although it comes from graphite—actually, it can be obtained by separating its layers—its properties and potential applications are very different.