Chapter U2.17, Problem 8E

Interpretation Introduction

Interpretation : Thechange in electrons in a polar covalent bond, a nonpolar bond and an ionic bond are to be explained.

Concept Introduction :

The tendency of an atom to attract shared electrons is called electronegativity. Chemists have assigned each atom a number called electronegativity value. This number represents the tendency of the atom to attract shared electrons. By comparing these numbers, we can compare the polarity of bonds. Bonds between atoms can be polar, nonpolar or ionic.

Answer to Problem 8E

When two atoms with different electronegativity valuesform a covalent bond with each other, the resultant bond is called polar covalent bond. The electrons are attracted more strongly towards one atom.

When the electronegativity values of the atoms that bond are identical/ similar, the resultant bond is a nonpolar covalent bond. In this bond, the electrons are shared equally between two atoms.

When the difference in electronegativity between two atoms is too large, the bond is no longer covalent but it becomes ionic. Theelectrons get pulled entirely towards one of the atoms.

Explanation of Solution

Polar covalent bond- In this type of bonding,the bonded pair of electrons is not shared equally among the atoms. Atoms that are more electronegative attract bonded electrons more strongly than atoms with less electronegative value. The bonded electrons move closer to the more electronegative atom. This results in formation of a partial negative charge and a partial negative charge on atoms.

Nonpolar bond- If in a diatomic molecule, the electronegativity value of both the atoms is equal or identical, there is no pulling of electrons and they share the electrons equally between them. In oxygen or hydrogen molecule both atoms have sameelectronegativity value. Hence the difference in value is zero and bond is nonpolar covalent.

Ionic bond- When the difference in electronegativity between two atoms is more than 2.1, the bond is no longer covalent but it becomes ionic. The electrons get transferred from less electronegative atom to more electronegative atom.

Conclusion

In a polar covalent molecule one atom pulls electrons more strongly than other atoms. In a nonpolar molecule both atoms have equal share of electrons. In ionic molecule, theelectrons are transferred to one atom.