The Heisenberg uncertainty principle requires that, since the energy ofthe electron is known, its exact position cannot be known. It is possibleto learn only the probable location of the electron in the vicinity of theatomic nucleus. An approximate description may begiven in terms of values of the quantum numbers n, l,and m. The shapes of the first few orbitals are shown inFigure 3-1 for the case of the hydrogen atom. This figure shows that, in general, an electron in the 1s orbitalis equally likely to be found in any direction about thenucleus. The maximum probablility is at a distance corresponding to the experimentally determined radius of the hydrogenatom. In contrast, in the case of an electron in a 2p orbital, there are threepossible values of the quantum number m. There are three possible regions in which the electron is most likely to be found. It is customary todepict these orbitals as being located along the cartesian (x, y, and z) axesof a three dimensional graph. Hence, the three probability distributionsare labeled px, py, and pz, respectively.
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