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In chemistry, an electron pair or Lewis pair consists of two electrons that occupy the same molecular orbital but have opposite spins. Gilbert N. Lewis introduced the concepts of both the electron pair and the covalent bond in a landmark paper he published in 1916. [1] [2]
1.602 176 634 × 10 −19 c [1] The elementary charge , usually denoted by e , is a fundamental physical constant , defined as the electric charge carried by a single proton (+1 e) or, equivalently, the magnitude of the negative electric charge carried by a single electron , which has charge −1 e .
In 1909 Robert A. Millikan provided a more accurate measurement of 1.5924 × 10 −19 C, only 0.6% off the current accepted measurement. Jean Perrin in 1909 measured the mass of hydrogen to be 1.43 × 10 −27 kg , [ 65 ] and if alpha particles are four times as heavy as that, they would have an absolute mass of 5.72 × 10 −27 kg .
[1] [2] [3] Introduced by Gilbert N. Lewis in his 1916 article The Atom and the Molecule, a Lewis structure can be drawn for any covalently bonded molecule, as well as coordination compounds. [4] Lewis structures extend the concept of the electron dot diagram by adding lines between atoms to represent shared pairs in a chemical bond.
Left: The dot-and-cross diagram of the LDQ structure of ozone (O 3). The nuclei are as indicated and the electrons are denoted by either dots or crosses, depending on their relative spins. Right: Simplified diagram of the LDQ structure of O 3, showing electrons in non-coincident pairs using thin lines and a coincident electron pair using a ...
Sten von Friesen measured the value with a new electron diffraction method, and the oil drop experiment was redone. Both gave high numbers. By 1937 it was "quite obvious" that Millikan's value could not be maintained any longer, and the established value became (4.800 ± 0.005) × 10 −10 statC or (1.6011 ± 0.0017) × 10 −19 C. [16]
In 1923, he formulated the electron-pair theory of acid–base reactions. In this theory of acids and bases, a "Lewis acid" is an electron-pair acceptor and a "Lewis base" is an electron-pair donor. [41] This year he also published a monograph on his theories of the chemical bond. [42]
An example is the muon, with a mean lifetime of 2.2 × 10 −6 seconds, which decays into an electron, a muon neutrino and an electron antineutrino. The electron, on the other hand, is thought to be stable on theoretical grounds: the electron is the least massive particle with non-zero electric charge, so its decay would violate charge ...