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Van Der Waals vs Hydrogen Bonds
"On the Comparison of Van der Waals Forces and Hydrogen Bonds"
Between heaven and earth, the formation of things is related to the force. Among them, the van der Waals force and the hydrogen bond clutch in the aggregation and dispersion of particles are particularly important and cannot be ignored.
The van der Waals force is a weak force that generally exists between molecules. It originates from the instantaneous dipole and the induced dipole of the molecule. The electron cloud in the molecule is not static, and the instantaneous distribution is uneven, resulting in an instantaneous dipole. This instantaneous dipole polarizes neighboring molecules and induces an induced dipole. The two attract, and the van der Waals force is formed. Although this force is small, it has a great impact on the physical properties of matter. For example, halogen elemental substances, from fluorine to iodine, the relative molecular weight increases gradually, and the van der Waals force also increases gradually, so the melting boiling point rises in sequence. At room temperature, fluorine and chlorine are gaseous, bromine is liquid, and iodine is solid. This is the effect of van der Waals force.
And hydrogen bonding is a special kind of intermolecular force. Its formation requires hydrogen atoms to be covalently bonded with atoms with large electronegativity and small radius (such as nitrogen, oxygen, and fluorine). Hydrogen atoms, because their electron clouds are strongly pulled towards electronegative large atoms, are almost naked protons, and can attract each other to the lone pair of electrons of another electronegative large atom, which is a hydrogen bond. The force of hydrogen bonding is stronger than van der Waals force. Taking water as an example, the existence of hydrogen bonds between water molecules makes the melting boiling point of water much higher than that of hydrogen sulfide. The relative molecular weight of hydrogen sulfide is greater than that of water. If only van der Waals forces are considered, the melting boiling point of water should be lower than that of hydrogen sulfide. However, due to hydrogen bonds, water is liquid at room temperature, and hydrogen sulfide is gaseous.
Compared with the two, van der Waals forces exist between various molecules, without the limitation of special atoms, and the size of the force is related to the relative molecular mass; hydrogen bonds require specific atoms to participate, and the force is stronger, which has a more significant impact on the properties of substances. The unique properties of many substances are due to the differences in their effects. It is helpful to understand the similarities and differences between van der Waals forces and hydrogen bonds in order to understand the microstructure and macroscopic properties of substances.
Between heaven and earth, the formation of things is related to the force. Among them, the van der Waals force and the hydrogen bond clutch in the aggregation and dispersion of particles are particularly important and cannot be ignored.
The van der Waals force is a weak force that generally exists between molecules. It originates from the instantaneous dipole and the induced dipole of the molecule. The electron cloud in the molecule is not static, and the instantaneous distribution is uneven, resulting in an instantaneous dipole. This instantaneous dipole polarizes neighboring molecules and induces an induced dipole. The two attract, and the van der Waals force is formed. Although this force is small, it has a great impact on the physical properties of matter. For example, halogen elemental substances, from fluorine to iodine, the relative molecular weight increases gradually, and the van der Waals force also increases gradually, so the melting boiling point rises in sequence. At room temperature, fluorine and chlorine are gaseous, bromine is liquid, and iodine is solid. This is the effect of van der Waals force.
And hydrogen bonding is a special kind of intermolecular force. Its formation requires hydrogen atoms to be covalently bonded with atoms with large electronegativity and small radius (such as nitrogen, oxygen, and fluorine). Hydrogen atoms, because their electron clouds are strongly pulled towards electronegative large atoms, are almost naked protons, and can attract each other to the lone pair of electrons of another electronegative large atom, which is a hydrogen bond. The force of hydrogen bonding is stronger than van der Waals force. Taking water as an example, the existence of hydrogen bonds between water molecules makes the melting boiling point of water much higher than that of hydrogen sulfide. The relative molecular weight of hydrogen sulfide is greater than that of water. If only van der Waals forces are considered, the melting boiling point of water should be lower than that of hydrogen sulfide. However, due to hydrogen bonds, water is liquid at room temperature, and hydrogen sulfide is gaseous.
Compared with the two, van der Waals forces exist between various molecules, without the limitation of special atoms, and the size of the force is related to the relative molecular mass; hydrogen bonds require specific atoms to participate, and the force is stronger, which has a more significant impact on the properties of substances. The unique properties of many substances are due to the differences in their effects. It is helpful to understand the similarities and differences between van der Waals forces and hydrogen bonds in order to understand the microstructure and macroscopic properties of substances.
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