Chapter U2.43, Problem 2E

Interpretation Introduction

Interpretation : Difference between a polar covalent bond and ionic bond is to be explained.

Concept Introduction :

A covalent bond is formed when there is sharing of electrons between the atoms to fulfill the noble gas configuration. An ionic bond is a chemical bond formed when one atom gains or loses electrons to complete the noble gas configuration. Both the bonds are polar in nature.

Answer to Problem 2E

When two atoms with different electronegativities form a covalent bond with each other, the resultant bond is called polar covalent bond. Example: HCl has polar covalent bond between hydrogen atom and chlorine atom.

When the electronegativities of the atoms that bond differ greatly, the electrons get pulled entirely towards one of the atoms. The resultant bond is anionic bond. Example: NaCl has ionic bond between sodium and chlorine atoms.

Explanation of Solution

In a polar molecule, the bonded pair of electrons is not shared equally among the atoms. For example in HCl molecule, the hydrogen and chlorine atom do not share the bonded pair of electrons equally. The tendency of an atom to attract shared electrons is called electronegativity. Atom with higher electronegativity attracts more electrons than atom with low electronegativity. Atoms that are more electronegative have partial negative charge and atoms that are less electronegative have positive charge. This results in formation of a polar covalent bond.

If in a molecule, one atom is highly electronegative than the other atom, it pulls the electrons completely toward itself forming oppositely charged ions called anion and cation. The metal atom forms the positive charge and nonmetal forms negative charge. The bond thus formed is called ionic bond. In NaCl molecule sodium develops positive charge while chlorine develops negative charge as it pulls the valence electron of sodium towards itself.

Conclusion

Ionic bonds are extremes of polar bonds in which electrons get transferred to the more electronegative atom in the pair.