Electronegativity is a measure of the tendency of an atom to attract a bonding pair of electrons. Linus Carl Pauling was an American chemist, biochemist, peace activist, author and an educator who gave the calculation of electronegativity first. Pauling’s scale of electro negativity is based on excess bond energies. For a heteropolar bond A-B, by assigning arbitrary value of electronegativity to one of the elements, the value of the other can be calculated. Pauling first proposed the concept of electronegativity as an explanation of the fact that the covalent bond between two different atoms (A– B) is stronger than would be expected by taking the average of the strengths of the A–A and B–B bonds. Linus Pauling’s scale was the most commonly used method for the calculation of electronegativity. This gives a dimensionless quantity, commonly referred to as the Pauling scale, on a relative scale running from around 0.7 to 3.98. Robert S. Mulliken proposed that the arithmetic mean of the first ionization energy and the electron affinity should be a measure of the tendency of an atom to attract electrons. Mulliken electronegativity can only be calculated for an element for which the electron affinity is known. Allred-Rochow electronegativity is a measure that determines the values of the electrostatic force exerted by the effective nuclear charge on the valence electrons. The higher the charge per unit area of atomic surface, the greater is the tendency of that atom to attract electrons. Sanderson’s electronegativity scale is based on the principle that the ability of an atom or ion to attract electrons to itself is dependent upon the effective nuclear charge felt by the outermost valence electrons. It is a well known fact that as the effective nuclear charge increases the size of the atom decreases. It becomes more compact.