Contrary to the well-known “planetary” model of electrons whirling around an atom’s nucleus as well-defined chunks of matter in circular or elliptical orbits, electrons in “orbit” don’t really act like pieces of matter at all. Rather, they exhibit the characteristics of both particle and wave, their behavior constrained by placement within distinct zones around the nucleus referred to as “shells” and “subshells.” Electrons can occupy these zones only in a limited range of energies depending on the particular zone and how occupied that zone is with other electrons. If electrons really did act like tiny planets held in orbit around the nucleus by electrostatic attraction, their actions described by the same laws describing the motions of real planets, there could be no real distinction between conductors and insulators, and chemical bonds between atoms would not exist in the way they do now.
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Conduction of electricity is nothing but moving of charge, which can be achieved by displacing charged particles. In conductors, the atoms have free electrons that are free to move. These moving electrons constute current. Conduction can also take place by displacing ions in a solution. Since humans are aware of only these two modes of conduction till date, only the elements having free electrons or the solutions having free ions are capable of conduction and not other substances.
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