Question

Using Figure, explain, in terms of Coulomb’s law, why a polar molecule (such as in Figure 18.43) is attracted by both positive and negative charges.

Short answer

Due to developed partial negative charge on more electronegative atom and partial positive charge on less electronegative atom, a polar molecule is attracted by both positive and negative charges.

Step-by-step solution

Polar molecule

Due to difference in electronegativity between bonded atoms in a molecule, the bonded electron shifts towards more electronegative atom creating partial negative charge on more electronegative atom and partial positive charge on less electronegative atom. Such molecules are known as polar molecules.

Coulomb’s law

Coulomb stated that when two-point charges are separated by some distance, a force of attraction or repulsion acts between them.

When water molecule is kept near to a positively charged body, the water molecule gets attracted to the positively charged body due to the presence of partial negative charge in the Oxygen atom.

When water molecule is kept near to a negatively charged body, the water molecule gets attracted to the negatively charged body due to the presence of partial positive charge in the Hydrogen atoms.

Hence, a polar molecule is attracted by both positive and negative charges.