Question

How does electronegativity affect the polarity of a bond between two atoms?

Answer 1

In a bond there are two atoms so an atom which is present at more right in the periodic table is said to be more electronegative and thus it will attract the shared pair of electrons towards itself. This increases the polarity of the bond and then the bond is said to be a polar bond. Take an example of hydrogen fluoride for your better understanding.

Complete step by step answer:
Firstly we will see that what is a covalent bond? A bond which is formed by sharing of electrons is called a covalent bond. We know that in the periodic table there are elements on the right hand side of the table which have higher electronegativity while on the left hand side, there are less electronegative. Electronegativity is a term used for the attraction of nucleus on its outermost electrons. This concept of electronegativity gives us ideas about a polar and a nonpolar bond. So electronegativity plays an important role when it is formed between two different atoms.

Let’s consider hydrogen fluoride $HF$, in this molecule hydrogen is less electronegative in nature while fluorine is more electronegative. Therefore the bond present between them is of course a covalent bond but it is called a polar covalent bond, we add polar word because of the electronegativity difference between them.

Another example is of hydrogen chloride gas $HCl$ , its fumes that we have read in our books are of white colour, here also there is a bond form between hydrogen and chlorine that is why we can call it a polar covalent compound. We can represent the variation of electronegativity by using delta charge. The atom which contains more delta negative charge is more electronegative in nature and will attract the electrons towards itself.
${H^{\partial + }} - {F^{\partial - }}$
${H^{\partial + }} - C{l^{\partial - }}$

Note: Electronegativity is higher for elements which are present in the right hand side of periodic table, like for example you have nitrogen, oxygen and fluorine. Among the three fluorines are present at the rightmost side in the periodic table hence we can say it is most electronegative among all. Electronegativity will decrease as size increases so on moving down the group, electronegativity decreases.