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preface to fifteenth edition

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4.56 SECTION 4<br />

4.7 MOLECULAR GEOMETRY<br />

TABLE 4.14<br />

SpatialOrientation of Common Hybrid Bonds<br />

On the assumption that the pairs of electrons in the valency shell of a bonded a<strong>to</strong>m in a molecule are arranged<br />

in a definite way which depends on the number of electron pairs (coordination number), the geometrical arrangement<br />

or shape of molecules may be predicted. A multiple bond is regarded as equivalent <strong>to</strong> a single bond as far<br />

as molecular shape is concerned.<br />

Coordination<br />

Number<br />

Orbitals<br />

Hybridized<br />

GeometricalArrangement<br />

Minimum<br />

Radius Ratio<br />

sp<br />

dp<br />

Linear<br />

2 p 2<br />

ds<br />

d 2<br />

Bent (angular)<br />

3<br />

sp 2<br />

Trigonalplanar 0.155<br />

ds 2<br />

p 3<br />

d 2 p<br />

Trigonalpyramidal<br />

sp 2 d<br />

p 2 d 2<br />

4 sp 3<br />

d 3 s<br />

d 4<br />

Square planar<br />

Tetrahedral0.225<br />

Tetragonalpyramidal<br />

5<br />

6<br />

sp 3 d<br />

d 3 sp<br />

d 2 sp 3<br />

d 4 sp<br />

Trigonalbipyramidal 0.155<br />

Octahedral0.414<br />

Trigonalprism<br />

7 One a<strong>to</strong>m above the face<br />

of an octahedron,<br />

which is dis<strong>to</strong>rted<br />

chiefly by separating<br />

the a<strong>to</strong>ms at the corners<br />

of this face.<br />

0.592<br />

8<br />

d 4 sp 3<br />

Square antiprism (dodecahedral)<br />

0.645<br />

Cube 0.732<br />

9<br />

Formed by adding a<strong>to</strong>ms<br />

beyond each of the<br />

verticalfaces of a right<br />

triangular prism.<br />

0.732<br />

12 Cube-octahedron 1.000

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