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Dispersion Forces Dipole Dipole Hydrogen Bonding Comparison
On the Comparison of Dispersion Force, Dipole-Dipole Force and Hydrogen Bond
The interaction force between matter is related to the fundamentals of physical properties. Among them, the dispersion force, the dipole-dipole force and the hydrogen bond have their own characteristics, which have significant effects on the microstructure and macroscopic performance. Try to discuss in detail.
Dispersion force exists between all molecules. It originates from the constant motion of electrons in the molecule and the vibration of the nucleus, causing the instantaneous positive and negative charge centers to not coincide, resulting in an instantaneous dipole. This instantaneous dipole induces neighboring molecules to produce induced dipoles, and the molecules generate mutual attraction. Although its force is weak, it is widely present, and it contributes greatly to the liquefaction of condensed matter of non-polar molecules, such as rare gases. Taking halogen elements as an example, from fluorine to iodine, the relative molecular weight gradually increases, the number of electrons increases, the molecular deformability increases, and the dispersion force also increases, so its melting point gradually increases.
The dipole-dipole force is more common between polar molecules. Polar molecules are inherently permanent dipoles, and the heteropoles between molecules attract and repel at the same pole, so this force is generated. Compared with the dispersion force, its effect is slightly stronger. For example, hydrogen chloride gas, hydrogen chloride molecules are polar molecules, and the intermolecular dipole-dipole force makes it easier to liquefy than the gas composed of non-polar molecules.
The hydrogen bond is a special kind of intermolecular force. When a hydrogen atom is covalently bonded to an atom with a large electronegativity and a small radius (such as fluorine, oxygen, and nitrogen), the hydrogen atom is nearly naked and can produce electrostatic attraction with another atom with a large electronegativity. This is known as hydrogen bonding. The force of hydrogen bonding is stronger than the dispersion force and the dipole-dipole force. Many unique properties of water, such as high melting boiling point and large specific heat capacity, depend on the work of hydrogen bonding. The density of ice is less than that of water, and it is also due to the fact that hydrogen bonding causes water molecules to form a regular tetrahedral structure in the solid state, which increases the molecular spacing.
In summary, the dispersion force is ubiquitous and the force is the weakest; the dipole-dipole force only exists between polar molecules, and the strength is second; the hydrogen bond is special and strong, which has a significant impact on the properties of substances. These three interact in different material systems to co-shape the diverse properties of substances.
The interaction force between matter is related to the fundamentals of physical properties. Among them, the dispersion force, the dipole-dipole force and the hydrogen bond have their own characteristics, which have significant effects on the microstructure and macroscopic performance. Try to discuss in detail.
Dispersion force exists between all molecules. It originates from the constant motion of electrons in the molecule and the vibration of the nucleus, causing the instantaneous positive and negative charge centers to not coincide, resulting in an instantaneous dipole. This instantaneous dipole induces neighboring molecules to produce induced dipoles, and the molecules generate mutual attraction. Although its force is weak, it is widely present, and it contributes greatly to the liquefaction of condensed matter of non-polar molecules, such as rare gases. Taking halogen elements as an example, from fluorine to iodine, the relative molecular weight gradually increases, the number of electrons increases, the molecular deformability increases, and the dispersion force also increases, so its melting point gradually increases.
The dipole-dipole force is more common between polar molecules. Polar molecules are inherently permanent dipoles, and the heteropoles between molecules attract and repel at the same pole, so this force is generated. Compared with the dispersion force, its effect is slightly stronger. For example, hydrogen chloride gas, hydrogen chloride molecules are polar molecules, and the intermolecular dipole-dipole force makes it easier to liquefy than the gas composed of non-polar molecules.
The hydrogen bond is a special kind of intermolecular force. When a hydrogen atom is covalently bonded to an atom with a large electronegativity and a small radius (such as fluorine, oxygen, and nitrogen), the hydrogen atom is nearly naked and can produce electrostatic attraction with another atom with a large electronegativity. This is known as hydrogen bonding. The force of hydrogen bonding is stronger than the dispersion force and the dipole-dipole force. Many unique properties of water, such as high melting boiling point and large specific heat capacity, depend on the work of hydrogen bonding. The density of ice is less than that of water, and it is also due to the fact that hydrogen bonding causes water molecules to form a regular tetrahedral structure in the solid state, which increases the molecular spacing.
In summary, the dispersion force is ubiquitous and the force is the weakest; the dipole-dipole force only exists between polar molecules, and the strength is second; the hydrogen bond is special and strong, which has a significant impact on the properties of substances. These three interact in different material systems to co-shape the diverse properties of substances.
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