Erwin Schrödinger

**Quantum Numbers (Erwin
Schrödinger)**

A powerful model of the atom was developed by Erwin Schrödinger in 1926. Schrödinger
combined the equations for the behavior of waves with the de Broglie equation to generate
a mathematical model for the distribution of electrons in an atom. The advantage of this
model is that it consists of mathematical equations known as *wave functions* that
satisfy the requirements placed on the behavior of electrons. The disadvantage is that it
is difficult to imagine a physical model of electrons as waves.

The Schrödinger model assumes that the electron is a wave and tries to describe the regions in space, or orbitals, where electrons are most likely to be found. Instead of trying to tell us where the electron is at any time, the Schrödinger model describes the probability that an electron can be found in a given region of space at a given time. This model no longer tells us where the electron is; it only tells us where it might be.

The Bohr model was a one-dimensional model that used one quantum number to describe the
distribution of electrons in the atom. The only information that was important was the *size*
of the orbit, which was described by the *n* quantum number. Schrödinger's model
allowed the electron to occupy three-dimensional space. It therefore required three
coordinates, or three quantum numbers, to describe the orbitals in which electrons can be
found.

The three coordinates that come from Schrödinger's wave equations are the principal (*n*),
angular (*l*), and magnetic (*m*) quantum numbers. These quantum numbers
describe the size, shape, and orientation in space of the orbitals on an atom.

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