handbook of carbon, graphite, diamond and fullerenes

26 Carbon, Graphite, Diamond, and Fullerenes
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S Orbital
P Orbital
Figure 2.6. Schematic representation of the "s" and "p" orbitais.
with its spin uncoupled from the other electrons. This alteration occurs as
a result of the formation of hybrid atomic orbitais, in which the arrangement
of the electrons of the L shell of the atom in the ground state is modified as
one of the 2s electron is promoted (or lifted) to the higher orbital 2p as shown
in Fig. 2.7. These new orbitais are called hybrids since they combine the
2s and the 2p orbitais. They are labeled sp 3 since they are formed from one
s orbital and three p orbitais.
In this hybrid sp 3 state, the carbon atom has four 2sp 3 orbitais, instead
of two 2s and two 2p of the ground-state atom and the valence state is raised
from two to four. The calculated sp 3 electron-density contour is shown in
Fig. 2.8 and a graphic visualization of the orbital, in the shape of an electron
cloud, is shown in Fig. 2.9. [12] This orbital is asymmetric, with most of it
concentrated on one side and with a small tail on the opposite side.