Chapter U2, Problem 7RE

Interpretation Introduction

Interpretation : The term dipole is to be explained and reason for the methane to have four dipoles but still no overall dipole is also to be explained.

Concept Introduction :

There are two classes of molecules; polar and nonpolar. There are partial charges on atoms of a polar molecule.One atom attracts the shared electrons more strongly than the other atom. Because of this, displacement of electrons one atom develops a partial negative charge and other atom develops a partial positive charge.

Answer to Problem 7RE

A polar molecule is called a dipole as it has two poles; a positive end and a negative end. The polar bond is also called a dipole.

In methane, CH₄ molecule, there are four dipoles present, each between C-H. Two pairs of dipoles in opposite direction in CH₄ balance each other, and there is no overall partial positive or negative charge on the molecule. So the overall molecule is nonpolar. Overall the methane molecule has no dipole.

Explanation of Solution

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 bond or a dipole. A polar molecule is called a dipole as it has two poles; a positive end and a negative end.

In methane, CH₄ molecule, there are four dipoles present, each between C-H. There is a difference in electronegativity values between carbon and hydrogen atoms. So carbon gets a partial negative charge while hydrogen gets a partial positive charge. Two pairs of dipoles in opposite direction in CH₄ balance each other, and there is no overall partial positive or negative charge on the molecule. So the overall molecule is nonpolar. Overall, the methane molecule has no dipole.

Conclusion

A polar molecule is called a dipole. When the dipoles balance each other in a molecule there is no overall dipole and the molecule becomes nonpolar.