Photodissociation | chemical reaction | Britannica (original) (raw)
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ocean formation
In ocean: Origin of the ocean waters Photodissociation (i.e., separation due to the energy of light) of water vapour into molecular hydrogen (H2) and molecular oxygen (O2) in the upper atmosphere allowed the hydrogen to escape and led to a progressive increase of the partial pressure of oxygen at Earth’s surface. The… Read More
In seawater: The early oceans …production of oxygen was by photodissociation of water in the atmosphere as a result of absorption of ultraviolet light. The reaction is 2H2O + hν = O2 + 2H2, in which hν represents a photon of ultraviolet light. The hydrogen produced would escape into space, and the O2 would react… Read More
ozone creation and destruction
In ozone layer: Ozone creation and destruction This process, called photodissociation, results in the release of single oxygen atoms, which later join with intact oxygen molecules to form ozone. Rising atmospheric oxygen concentrations some two billion years ago allowed ozone to build up in Earth’s atmosphere, a process that gradually led to the formation of… Read More
photochemical reactions
In photochemical reaction: Photodissociation One type of photochemical reaction is the dissociation of a molecule into two fragments. Since it is the electrons that provide the bonding forces that hold atoms together into molecules, if the distribution of electrons within a molecule changes drastically, the bonding forces may… Read More
