Calculate van der Waals force
Van der Waals force is the intermolecular force, also known as van der Waals force. It is a kind of weak basic electric attraction existing between neutral molecules or atoms. The intermolecular force (van der Waals force) has three sources:
1, and the interaction between the permanent dipole moments of polar molecules
2. One polar molecule polarizes the other, proces inced dipole moment and attracts each other
The motion of electrons in the molecule proces instantaneous dipole moment, which makes the adjacent molecule instantaneous polarization, and the latter in turn enhances the instantaneous dipole moment of the original molecule The contribution of these three forces is different, and usually the third one is the largest{rrrrrrr}
extended data:
classification
1, dispersion force
dispersion force (also known as "London force") exists between all molecules or atoms. It is the force between the instantaneous dipoles of molecules, that is, e to the movement of electrons, the position of the instantaneous electron is asymmetric to the nucleus, that is to say, the center of gravity of positive charge and the center of gravity of negative charge do not coincide instantaneously, resulting in the instantaneous dipole
Orientation force (also known as dipole dipole force) orientation force occurs between polar molecules and polar molecules. Due to the uneven electrical distribution of polar molecules, one end is positively charged and the other is negatively charged, forming a dipole 3, the relationship between the three forces
there are orientation force, inction force and dispersion force between polar molecules; There are inced and dispersive forces between polar and nonpolar molecules; There is only dispersive force between nonpolar molecules and nonpolar molecules
van der Waals force can be divided into three forces: incing force, dispersing force and orientating force
van der Waals force is an attractive force existing between molecules, which is much weaker than the chemical bond. Generally speaking, the greater the van der Waals force of a substance, the higher its melting point and boiling point. For substances with similar composition and structure, the van der Waals force generally increases with the increase of relative molecular mass< The van der Waals force is also called intermolecular force. Molecular substances can change from gaseous state to liquid state, from liquid state to solid state, which indicates that there is interaction between molecules, which is called intermolecular force or van der Waals force. There are three sources of intermolecular forces: dispersion force, inction force and orientation force. The dispersive force is the force between the instantaneous dipoles of molecules, and its magnitude is related to the deformation of molecules and other factors. Generally, the larger the molecular weight is, the more electrons are contained in the molecule, the greater the deformability of the molecule and the greater the dispersion force. The inced force is the force between the intrinsic dipole and the inced dipole of a molecule, and its magnitude is related to the polarity and deformability of the molecule. Orientation force is the force between the inherent dipoles of a molecule, and its magnitude is related to the polarity and temperature of the molecule. The greater the dipole moment of polar molecules, the greater the orientation force; The higher the temperature, the smaller the orientation force
dispersion, inction and orientation forces between polar molecules; The dispersion and inction forces between polar and nonpolar molecules; There is only a dispersive force between nonpolar molecules. The experimental results show that for most molecules, the dispersion force is the main factor; Only the molecules with large dipole moment (such as water) have the main orientation force; And the incing force is usually very small<
the third van der Waals force
in the aggregation state of matter, there is a weak attraction between molecules, the size of the interaction energy is generally only a few kilojoules to tens of kilojoules per mole, which is 1-2 orders of magnitude smaller than the bond energy of chemical bonds, also known as van der Waals gravity or van der Waals force. It consists of three parts: 1. When polar molecules are close to each other, their inherent dipoles will repel each other and attract each other. They will be aligned in a directional way, resulting in intermolecular force, which is called orientation force. The larger the dipole moment is, the larger the orientation force is. ② When the polar molecules and nonpolar molecules are close to each other, the nonpolar molecules will polarize under the action of the intrinsic dipole of the polar molecules to proce the inced dipole, and then the inced dipole and the intrinsic dipole will attract each other to proce the intermolecular force, which is called the inced force. Of course, there are also inctive forces between polar molecules. ③ Between nonpolar molecules, e to the constant motion of the positive and negative particles of the constituent molecules, the instantaneous positive and negative charge gravity centers do not coincide, resulting in the instantaneous dipole. The interaction between these instantaneous dipoles is called dispersion force. The larger the molecular weight is, the larger the dispersion force is. Of course, there are also dispersion forces between polar and nonpolar molecules or between polar molecules. Van der Waals gravity is a kind of force existing between molecules, which has no directionality and saturation, and has an action range of hundreds of Pico meters. It has a decisive influence on the physical and chemical properties of substances, such as boiling point, melting point, heat of gasification, heat of melting, solubility, surface tension and viscosity.
Van der Waals force includes orientation force, inction force and dispersion force
orientation force (also known as dipole dipole force) orientation force occurs between polar molecules. Due to the uneven electrical distribution of polar molecules, one end is positively charged and the other is negatively charged, forming a dipole
inction force existed between polar and nonpolar molecules, and between polar and polar molecules. The electron cloud of nonpolar molecules is deformed e to the influence of electric field generated by dipole of polar molecules on nonpolar molecules
dispersion force (also known as "London force") exists between all molecules or atoms. It is the force between the instantaneous dipoles of molecules, that is, e to the movement of electrons, the position of the instantaneous electron is asymmetric to the nucleus, that is to say, the center of gravity of positive charge and the center of gravity of negative charge do not coincide instantaneously, resulting in the instantaneous dipole
Extended data:
the proportion of these three types of forces depends on the polarity and deformability of the interacting molecules. The larger the polarity is, the more important the orientation force is; The larger the deformability is, the more important the dispersion force is; Incement is related to both factors
But for most molecules, the dispersion force is the main one. The experimental results show that for most molecules, the dispersion force is the main factor; Only the molecules with large dipole moment (such as water) have the main orientation force; And the incing force is usually very smallelectrostatic force: it is the gravitational force between polar molecules
inced force: the interaction between the permanent dipole of a polar molecule and its inced dipole on other molecules
the dispersive force is the interaction between the instantaneous dipoles of molecules
the van der Waals force has no saturation and directionality, and exists permanently among all molecules.
van der Waals force can be divided into three types: inced force, dispersive force and orientation force. They are not the same force as Coulomb force, but they are all electrical in nature, belonging to the electromagnetic interaction among the four basic cosmic interactions (strong interaction, weak interaction, electromagnetic interaction and universal gravitation). Coulomb force is an electrostatic force. It is inaccurate to say that it is the force of charged particles. This is the difference between Coulomb force and van der Waals force. The charge of van der Waals force can move
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and related entries of Internet van der Waals
when the polar group is close to each other, when the distance is less than 0.5nm, the interaction among atoms, molecules or atomic groups will inevitably occur, resulting in intermolecular force, which is called van der Waals force
solid surface can adsorb liquid and gas e to van der Waals force, which is called physical adsorption. Van der Waals force includes couple force, inced force and dispersive force, which can be divided into the following cases:
electrostatic force is the gravitational force between polar molecules
inced force: the interaction between the permanent dipole of a polar molecule and its inced dipole on other molecules
the dispersive force is the interaction between the instantaneous dipoles of molecules
the van der Waals force has no saturation and directionality, and exists permanently among all molecules.