Oxygen
Article
May 19, 2022
Oxygen (lat. Oxygenium, from the Greek ὀξύς ‚oxys - sharp, acidic and γεννάω‚ gene - that creates, ie the one that creates acid) is a chemical element denoted by the symbol O and has atomic number 8. In the periodic table it is located in the sixth main group, ie it belongs to chalcogenic non-metals. It is the most widespread element in the Earth's crust with a share of 48.9% to 49.4%, or about 30% by weight, making it the second most common after iron. It also makes up 20.8% of the Earth's atmosphere. In its elemental form, oxygen predominantly appears as a covalent homodimer, i. as a compound of two atoms of summary formula O2, meaning molecular oxygen, dioxygen or dioxygen. It is a colorless gas without odor and taste, and in clean air it is represented by about 20.942%. It is necessary for combustion and corrosion. It is needed for the life of almost all living beings on Earth. It is created by plants in the process of photosynthesis, but they also consume it for respiration, although to a lesser extent in relation to the amount they produce by photosynthesis. For respiration, plants take oxygen directly from the air or by resorption from water (dissolved oxygen). In high concentrations, oxygen is poisonous to most living things. A metastable, highly reactive allotropic form of oxygen with three oxygen atoms O3 is called ozone. Atomic oxygen, ie oxygen in the form of free, individual atoms, is stable only under extreme conditions, for example in a vacuum in space or in hot atmospheres of stars. It has a certain significance as an intermediate in many reactions in the chemistry of the atmosphere. Stable isotopes are 16O, 17O and 18O