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Electron transfer (ET) occurs when an electron relocates from an atom, ion, or molecule, to another such chemical entity. ET describes the mechanism by which electrons are transferred in redox reactions. [2] Electrochemical processes are ET reactions.
An electron transport chain (ETC [1]) is a series of protein complexes and other molecules which transfer electrons from electron donors to electron acceptors via redox reactions (both reduction and oxidation occurring simultaneously) and couples this electron transfer with the transfer of protons (H + ions) across a membrane.
The strongest bonds are formed by the sharing or transfer of electrons between atoms, allowing the formation of molecules. [17] Within a molecule, electrons move under the influence of several nuclei, and occupy molecular orbitals; much as they can occupy atomic orbitals in isolated atoms. [128]
The electrons are then transferred through a series of iron–sulfur clusters: the second kind of prosthetic group present in the complex. [20] There are both [2Fe–2S] and [4Fe–4S] iron–sulfur clusters in complex I. As the electrons pass through this complex, four protons are pumped from the matrix into the intermembrane space.
During forward electron transfer, only very small amounts of superoxide are produced (probably less than 0.1% of the overall electron flow). [53] [54] [55] During reverse electron transfer, complex I might be the most important site of superoxide production within mitochondria, with around 3-4% of electrons being diverted to superoxide ...
Electrons are transferred from iron, reducing oxygen in the atmosphere into water on the cathode, which is placed in another region of the metal. O 2 (g) + 4 H + (aq) + 4 e − → 2 H 2 O (l) Global reaction for the process:
Thus, generally, the d electrons in transition metals behave as valence electrons although they are not in the outermost shell. For example, manganese (Mn) has configuration 1s 2 2s 2 2p 6 3s 2 3p 6 4s 2 3d 5 ; this is abbreviated to [Ar] 4s 2 3d 5 , where [Ar] denotes a core configuration identical to that of the noble gas argon .
The numbers of electrons correspond to full shells in the quantum theory of the atom; the outer shell of a carbon atom is the n = 2 shell, which can hold eight electrons, whereas the outer (and only) shell of a hydrogen atom is the n = 1 shell, which can hold only two. [9]