Energy Of An Electron?
Energy Of An Electron: Since electronics deals with small particles called electrons, these tiny particles require a more detailed study. As discussed before, an electron is a negatively charged particle having nearly zero mass. Some of the important most properties of an electron are :
- Charge on an electron, e = 1.602 × 10−19 coulomb
- Mass of an electron, m = 9.0 × 10−31 kg
- Radius of an electron, r = 1.9 × 10−15 metre
The ratio e/m of an electron is 1.77 × 1011 coulombs/kg. This actually means that the mass of an electron is very small as compared to its charge. It’s because of this property of an electron that it is very mobile and is huge influenced by electric or magnetic fields.
Energy of an Electron
An electron rotating around the nucleus possesses two kinds of energies viz. kinetic energy because of its motion and potential energy because of the charge on the nucleus. The net energy of the electron is the sum of these two energies. The energy of an electron increases when its distance from the nucleus increases. Thus, an electron in the second orbit has more energy than the electron in the first orbit; electron in the third orbit has larger energy than in the second orbit. It is clear that electrons in the last orbit must have very high energy as compared to the electrons in the internal orbits. These last orbit electrons play a very important role in finding the physical, chemical, and electrical properties of a material.
The electrons in the outermost orbit of an atom are called valence electrons. The outermost orbit can carry a maximum of 8 electrons. The valence electrons define the physical and chemical properties of a matter. These valence electrons determine whether or not the material is chemically active; metal or non-metal or, gas or solid. These electrons also explain the electrical properties of a material. On the basis of current conductivity, materials are normally classified into conductors, insulators, and semiconductors. As a rough rule, one can determine the electrical behavior of material from the number of valence electrons as under :
(i) Whenever the number of valence electrons of an atom is less than four (i.e. half of the maximum
eight electrons), the material is normally metal and a conductor. Examples are sodium, magnesium, and aluminum which have one, two, and three valence electrons respectively (See Fig. 1.5).
(ii) Whenever the number of valences shell electrons of an atom is more than four, the material is normally a non-metal and an insulator. Examples are nitrogen, sulfur, and neon which have five, six, and eight valence electrons respectively (See Fig. 1.6).
(iii) Whenever the number of valences shell electrons of an atom is four (i.e. exactly one-half of the maximum 8 electrons), the material has both properties of metal and non-metal and is usually a semiconductor. Examples are carbon, silicon, and germanium (See Fig. 1.7).
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