8. The Machinery Behind The      Periodic Table   Previous PageNext Page
     Quantum Levels and Atomic Buildup

Neon has both the n = 1 and n = 2 orbitals completely occupied, and the electronic configuration is 1s 2s 2p. This is a more elaborate (and more informative) version of the configuration that was given in Chapter 3 as merely Ne 2,8.

There is one difference between the diagrams on these pages and previous diagrams. Carbon, for example, was shown with four unpaired electrons, rather than the 2s 2p configuration shown on the previous page.


Because the energy difference between s and p orbitals is small, and since two electrons in the same s orbital repel one another, the actual difference in energy between the two arrangements is small. Isolated carbon atoms in the gas phase do have the paired 2s2p configuration, but carbon atoms involved in tetrahedral bonding can be thought of as adopting the unpaired 2s 2p arrangement before the bonds are formed. The small cost in energy is more than compensated for by the extra stability of the bonds.

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