The liquid drop model of the nucleus was first proposed by Niels Bohr and F.Kalcar in the year 1937. They observed that there exists many similarities between the drop of a liquid and a nucleus. For instance,
- Both the liquid drop and the nucleus posses constant density
- The constant binding energy per nucleon of a nucleus is similar to the latent heat of vaporization of a liquid
- The evaporation of a drop corresponds to the radioactive properties of the nucleus
- The condensation of drops bears resemblance with the formation of compound nucleus, etc.
According to this model, the nucleus is supposed to be spherical in shape in the stable state with radius R=r0A1/3, just as a liquid drop is spherical due to symmetrical surface tension forces. The surface tension effects are analogous to the potential barrier effects on the surface of the nucleus.
- The density of a liquid drop is independent of the volume, as is the case with the nucleus. But whereas the nuclear density is independent of the type of nucleus, the density of a liquid does depend on its nature.
- Like the nucleons inside the nucleus, the molecules in the liquid drop interact only with their immediate neighbours.
- The non independence of the binding energy per nucleon on the number of nucleons in the nucleus is analogous to the non-independence of the heat of vaporisation of a liquid drop on the size of the drop.
- Molecules in a liquid drop evaporate from the liquid surface in raising the temperature of the liquid due to their increased energy of thermal agitation. Analogously, if high energy nuclear projectiles bombard the nucleus, a compound nucleus is formed in which the nucleons quickly share the incident energy and the emission of nucleons occurs.
- The phenomenon of nuclear fission is easily explained as the splitting of the liquid drop into two more or less equal parts if set into vibration with sufficient energy.
