Question

Why is oxygen written as $O_2$? Can anyone please explain to me why it is that in the periodic table oxygen is written as just O, but elsewhere it is written as $O_2$?

Answer 1

The energy metabolism of living creatures relies heavily on dioxygen. Photolysis of water during photosynthesis in cyanobacteria, green algae, and plants produces free oxygen in the biosphere. We take in oxygen as well as a small amount of carbon dioxide. We breathe out less oxygen but more carbon dioxide than we intake when we exhale.

Complete answer:
Each element's symbol is included just once in the Periodic Table. Molecules make up the oxygen we breathe. Because each molecule is made up of two oxygen atoms linked together, its formula is $O_2$.
The distinction between oxygen (O) and oxygen ($O_2$) is that the former is an oxygen atom, whilst the latter is a molecule made up of two O atoms bonded together. The most common form of oxygen is as a diatomic gas. As a result, we refer to it as $O_2$.
According to Avogadro, hydrogen and oxygen are diatomic molecules. If this is the case, the following is the reaction that results in the production of water: $2H_2O$ = 2$H_2$ + $O_2$
Because atomic nascent oxygen is exceedingly unstable in nature and cannot survive alone, $O_2$ is made up of two atoms of oxygen present in nature. $O_2$ is a gas, not a substance. It is a Molecular form of the Oxygen Element. Oxygen gas is a 'element molecule' or simply a 'element'.
It's true that Oxygen is abbreviated as O. One oxygen atom, on the other hand, cannot survive on its own since it is unstable. In order for an atom to be stable, it usually requires 8 electrons in its outer orbit. As a result, it forms a stable bond with another oxygen atom by sharing two electrons.

Note:-
When you cool oxygen to -183°C, it turns into a liquid. Rockets, notably the Rocket Lab's Electron rocket, employ liquid oxygen as a propellant. At temperatures below -218.79°C, oxygen solidifies. The substances are transparent with a bright sky-blue colour in both their liquid and solid phases.