# Question #ee46a

##### 1 Answer

#### Answer:

The "planetary orbit" system of Bohr, even with its quantum energy levels could not survive the coming of quantum mechanics. Details follow...

#### Explanation:

Even as early as the 1910s, physicists were aware that there were problems with Bohr's circular orbit model of the quantum atom. By 1921, it had been suggested that particles such as electrons might possess wave-like properties.

In the late 1920s, Werner Heisenberg and Erwin Schroedinger separately created entirely new systems for describing the behaviour of electrons in atoms.

Heisenberg's Uncertainty Principle convinced scientists that it was impossible to know the location and the momentum of the electron with complete precision at the same moment.

Students of physics will realize that these quantities are just what is required if one it to plot a trajectory for a particle (such as the path of a projectile).

Therefore, according to the new quantum mechanics of the late 20s, it is no longer possible to describe any sort of path that the electron follows. Instead, Schroedinger's quantum mechanics described the electron's wavefunction as a mathematical construct that contained all the information relevant to the electron in an atom. It is the wavefunction, and the orbitals that it gives rise to that now describe the behaviour of the electron.

They do so not by describing a path for the electron, but by indicating the regions in space about the nucleus in which the electron is most likely to be found, and by describing the symmetries in the behaviour of the electrons of an atom.

And so, Bohr's model, while simple, and still remarkably useful in many ways cannot be taken as an accurate description of electron behaviour in atoms. For that, you must grasp the concept of the orbital.