scale relating the abilities of elements to attract electrons when their atoms are combined. For this purpose, the concept of electronegativity is introduced.

The electronegativity of an element is defined as the relative tendency of its atom to attract electrons towards it self when it is bonded to the atom of another element.

All the factors that influence the ionization energy and the electron affinity of elements influence the electronegativity values of those elements. Because of this, Milliken proposed that the electronegativity of an element is the average value of its ionization energy and electron affinity.

Electronegativity = ionization energy + electron affinity/2

Pauling assigned the electronegativity values for elements on the basis of bond energies. He assumed that the electronegativity of hydrogen is 2.20 and calculated the values of other elements with respect to hydrogen. Observe the values in the following example

Table-9
Period/group Element (electronegativity with respect to hydrogen)
Halogens: F(4.0), Cl(3.0), Br(2.8), I(2.5)
2nd period: Li(1.0), Be(1.47), B(2.0), C(2.5), N(3.0), O(3.5), F(4.0), Ne(-)

Electronegativity values of elements decrease as we go down in a group and increase along a period from left to right. The most electronegative element is ‘F’ and t>

Metallic and Non-Metallic Properties

Metals generally show less electronegative character. In compounds, they generally show a tendency to remain as positive ions. This property is often termed as electropositive character. Metals are electropositive elements.

Non metals are generally more electronegative due to their smaller atomic radii.

Let us examine the elements of 3rd period.

3rd period: Na     Mg     Al     Si     P     S     Cl

We know that Na and Mg are metals, Al and Si are semi metals (metalloids), P, S and Cl are non metals. So we find metals on left side and


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