The order of intermolecular forces from weakest to strongest is London forces, dipole-dipole forces, and hydrogen bonds. Dipole-dipole forces involve attractions between positive and negative regions of polar molecules. London forces are temporary dipole attractions, while hydrogen bonds specifically occur between hydrogen and electronegative atoms.
A. The correct order from weakest to strongest for the three types of intermolecular forces is:
- London forces (weakest)
- Dipole-dipole forces
- Hydrogen bonds (strongest)
1. London forces, also known as dispersion forces, are the weakest intermolecular forces. They are present in all molecules, whether polar or nonpolar, and are caused by temporary fluctuations in electron distribution, creating temporary dipoles. These temporary dipoles induce other molecules to have temporary dipoles as well, resulting in weak attractions between them.
2. Dipole-dipole forces are stronger than London forces and occur between polar molecules. In polar molecules, there is a permanent dipole moment due to the electronegativity difference between atoms. The positive end of one polar molecule is attracted to the negative end of another polar molecule, creating dipole-dipole interactions.
3. Hydrogen bonds are the strongest intermolecular forces. They are a special type of dipole-dipole interaction that occurs when hydrogen is bonded to highly electronegative atoms like nitrogen, oxygen, or fluorine. The hydrogen atom in one molecule forms a bond with the electronegative atom in another molecule, resulting in a strong attraction.
B. The correct types of intermolecular forces for each description are:
1. Dipole-dipole forces are an attraction between a positive region of a polar molecule and a negative region of another polar molecule.
2. London forces are attractions between temporary dipoles.
3. Hydrogen bonds are attractions between the H of one molecule and an electronegative atom on another molecule.