Neon has both the n
= 1 and n = 2 orbitals completely occupied, and the
electronic configuration is 1s
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
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
arrangement before the bonds are formed. The small cost in energy
is more than compensated for by the extra stability of the bonds.