on N. An sp hybridization scheme is appropriate for both C
and N; it is consistent with the linear arrangement of atoms
around C and with the placement of the lone pair on N as far
away as possible from the bonding electrons. Figure 4.9b
shows the -bonding framework in HCN (each region of
orbital overlap is occupied by a pair of electrons) and the
outward-pointing sp hybrid on N that accommodates the
lone pair. If we arbitrarily define the HCN axis as the z