The Plum Pudding Model is an atom model proposed by JJ Thomson, the physicist who discovered the electron. It is also known as the Chocolate Chip Cookie or Blueberry Muffin Model. You can easily picture it by imagining the said goodies. For example, you can imagine a plum pudding wherein the pudding itself is positively charged and the plums, dotting the dough, are the negatively charged electrons. Thus, in contrast to today's atom that has a very dense and very small (compared to the whole atom) positively charged nucleus, Thomson's had a more dispersed positive charge. As a whole, the plum pudding representation only strived to explain why most atoms were neutral. It's interesting to note that this model was sometimes visualized as having a cloud of positive charge, a striking contrast to the most recent atomic model which describes the positive nucleus to be surrounded by an electron cloud.

The Planetary Model of the atom has an atom consisting of a small, positively- charged nucleus orbited by negatively-charged electrons. Here's a closer look at the Planetary Model, also called the Bohr Model or the Rutherford-Bohr Model. The Bohr Model is a planetary model in which the negatively-charged electrons orbit a small, positively-charged nucleus similar to the planets orbiting the Sun (except that the orbits are not planar).

Main Points of the Bohr Model

 Electrons orbit the nucleus in orbits that have a set size and energy.  The energy of the orbit is related to its size. The lowest energy is found in the smallest orbit.  Radiation is absorbed or emitted when an electron moves from one orbit to another.

Electron Cloud Model As we all know, electrons are found to orbit around the nucleus of an atom. Each orbital in an atom is equivalent to an energy level of the electron. On absorbing a photon (ray of colored light), an electron moves to a higher level of energy. On similar lines, an electron can fall to a lower energy level by emitting a photon (ray of colored light), thus radiating energy.

The term, ‘electron cloud’ was used by the Noble Prizewinner Richard Feynman, an American physicist, in The Feynman Lectures on Physics. The model provides the means of visualizing the position of electrons in an atom. What is an electron cloud model? It is a visual model that maps the possible locations of electrons in an atom. The model is used to describe the probable locations of electrons around the nucleus. The electron cloud is also defined as the region where an electron forms a three-dimensional cloud around the nucleus, one that does not move relative to the atomic nucleus.