| 单词 | electron |
| 释义 | electron An elementary particle, classed as a lepton, with a rest mass (symbol me) of 9.109 3897(54) × 10-31 kg and a negative charge of 1.602 177 33(49) × 10-19 coulomb. Electrons are present in all atoms in groupings called shells around the nucleus; when they are detached from the atom they are called free electrons (see free electron theory). The antiparticle of the electron is the positron . The electron was discovered in 1897 by Joseph John Thomson. The problem of the structure (if any) of the electron is unsolved. If the electron is taken to be a point charge, its self-energy is infinite and difficulties arise for the Dirac equation. It is possible to give the electron a nonzero size with a radius r0, called the classical electron radius , given by r0 = e2/(mc2) = 2.82 × 10-13 cm, where e and m are the charge and mass respectively of the electron and c is the speed of light. This model also causes difficulties, such as the necessity of postulating Poincaré stresses. It is now thought that the problems associated with the electron need to be analysed using quantum electrodynamics rather than classical electrodynamics (see classical field theory) |
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