classification
Dipoles can be divided into three categories:
permanent dipole ： Polar molecule Due to different composition elements, the ability of attracting electrons varies（ Periodic law of elements ）This causes the electron in the molecule to shift, which produces polarity, and the dipole persists, which is called the inherent dipole. Induced dipole : means Nonpolar molecule In electric field or other Polar molecule In the case of closer distance negative electricity ， Nuclear band positive electricity , they will shift, which is called induced dipole. instantaneous dipole : All molecules, whether polar or non-polar, Nucleus It vibrates all the time. Electrons move and jump all the time. When they move, they leave occasionally Balance position The polarity is generated, but the duration of this process is very short, so it is called instantaneous dipole. 
