Electron cloud is an informal way to describe an atomic orbital.
The electron cloud is not really a thing. An electron cloud model is different from the older Bohr atomic model by Niels Bohr. Bohr talked about electrons orbiting the nucleus. Explaining the behavior of these electron "orbits" was a key issue in the development of quantum mechanics.
The electron cloud model says that we cannot know exactly where an electron is at any given time, but the electrons are more likely to be in specific areas. In the Bohr model, electrons were assigned to different shells. These shells explained the repeating patterns of chemical properties in the periodic table. Using quantum mechanics, chemists can use the electron cloud model to assign electrons to different atomic orbitals. These atomic orbitals are not all spheres. Atomic orbitals also explain the patterns in the periodic table.
The electron cloud model was developed in 1926 by Erwin Schrödinger and Werner Heisenberg. The model is a way to help visualize the most probable position of electrons in an atom. The electron cloud model is currently the accepted model of an atom.
According to Bohr's calculations for a hydrogen atom, the electron under normal conditions always stays at a distance of 0.529Å from the nucleus. But according to wave mechanical or cloud concept model, the electron keeps on moving away or towards the nucleus and the maximum probability of locating it lies at a distance of 0.529Å from the nucleus. In other words, the radius of electron cloud or radius of maximum probability is 0.529Å.
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