Key Difference – Ion Dipole vs Dipole Dipole Forces
Intermolecular forces are the attraction forces exist between different molecules. Ion-dipole forces and dipole-dipole forces are two forms of intermolecular forces. Some other examples for intermolecular forces include ion-induced dipole forces, hydrogen bonds, and Van der Waal forces. These forces are electrostatic attractions because the molecules are attracted based on their electrical charges. The key difference between ion-dipole and dipole-dipole forces is that ion-dipole forces exist between ionic species and polar molecules whereas dipole-dipole forces exist between polar molecules.
CONTENTS
1. Overview and Key Difference
2. What is Ion Dipole Forces
3. What is Dipole Dipole Forces
4. Similarities Between Ion Dipole and Dipole Dipole Forces
5. Side by Side Comparison – Ion Dipole vs Dipole Dipole Forces in Tabular Form
6. Summary
What is Ion Dipole Forces?
Ion-dipole forces are attraction forces between ionic species and polar molecules.The ionic species can be an anion (a negatively charged species) or a cation (a positively charged species).A polar molecule is any molecule that has a permanent electrical charge separation within the molecule due to differences between electronegativity values of the atoms in that molecule. Electronegativity is the ability to attract electrons. When an atom having a high electronegativity is bonded to an atom having a low electronegativity, the bond electrons are attracted by the atom having the high electronegativity (then it gets a partial negative charge), giving the less electronegative atom a partial positive charge. This state of charge separation is called polarization and the molecule is called a polar molecule.
Ion-dipole forces are stronger than dipole-dipole forces. That is because this type of intermolecular force involves ionic species that has a higher electrical charge compared to a polar molecule. The ion-dipole forces are even stronger than hydrogen bonding. This interaction occurs due to electrostatic interactions between ion and dipole.
Figure 01: Hydration of Metal Ions occurs due to the attraction between Metal Ion and Water Molecules (dipole)
A subcategory of ion-dipole forces is ion-induced dipole forces that involve a nonpolar molecule instead of a polar molecule. A nonpolar molecule has no dipole (no charge separation). The charge of ion causes the nonpolar molecule to get polarized by distorting the electron cloud of the nonpolar molecule.
What are Dipole Dipole Forces?
Dipole-dipole forces are intermolecular forces that occur between polar molecules. These are electrostatic forces. When forming this type of force, the polar molecules tend to be aligned so that the attraction between the molecules is maximized by reducing the potential energy. This alignment also reduces the repulsions between the molecules.
Figure 02: Attraction Force Between Polar HCl Molecules
When a series of compounds with similar molar masses are considered (which have dipole-dipole interaction forces between molecules) the strength of dipole-dipole forces increases as the polarity increases. That happens because when the polarity is high, it means the charge separation is high. When the molecule has a high charge separation (high charged positive and negative terminals in the same molecule), it tends to strongly attract opposite charges. This also leads to increase the boiling point of compounds. Greater the dipole-dipole forces, greater the boiling point.
What are the Similarities Between Ion Dipole and Dipole Dipole Forces?
- Both Ion Dipole and Dipole Dipole Forces are types of intermolecular interactions
- Both Ion Dipole and Dipole Dipole Forces are electrostatic forces
What is the Difference Between Ion Dipole and Dipole Dipole Forces?
Ion Dipole vs Dipole Dipole Forces |
|
| Ion dipole forces are attractive forces between ionic species and polar molecules. | Dipole-dipole forces are intermolecular forces that occur between polar molecules. |
| Strength | |
| Ion-dipole forces are stronger than hydrogen bonds and dipole-dipole forces. | Dipole-dipole forces are weaker than hydrogen bonds and ion-dipole forces. |
| Components | |
| Ion-dipole forces arise between ions (cations or anions) and polar molecules. | Dipole-dipole forces arise between polar molecules. |
Summary – Ion Dipole vs Dipole Dipole Forces
Ion-dipole forces and dipole-dipole forces are intermolecular forces that exist between different chemical species such as cations, anions, and polar molecules. Polar molecules are covalent compounds having dipoles (electrical charge separations). A polar molecule has a positively charged terminal and a negatively charged terminal in the same molecule. Therefore, these terminals can have electrostatic attractions with opposite charges. The difference between ion-dipole and dipole-dipole forces is that ion-dipole forces exist between ionic species and polar molecules whereas dipole-dipole forces exist between polar molecules.
Reference:
1.“11.3: Dipole-Dipole Forces.” Chemistry LibreTexts, Libretexts, 11 Feb. 2018. Available here
2.Dipole-Dipole Forces. Available here
3.“Intermolecular Force.” Wikipedia, Wikimedia Foundation, 14 Mar. 2018. Available here
Image Courtesy:
1.’Na+H2O’By Taxman (Public Domain) via Commons Wikimedia
2.’Dipole-dipole-interaction-in-HCl-2D’By Benjah-bmm27 – Own work, (Public Domain) via Commons Wikimedia
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