4.7

MOLECULAR GEOMETRY

TABLE 4.14

Spatial Orientation of Common Hybrid Bonds

On the assumption that the pairs of electrons in

the valency shell of a bonded atom in a molecule are arranged

in a definite way which depends on the number of electron pairs (coordination number), the geometrical arrange-

ment or shape of molecules may be predicted. A multiple bond is regarded as equivalent to a single bond as far

as molecular shape is concerned.

Coordination

Orbitals

Minimum

Number

Hybridized

Geometrical Arrangement

Radius Ratio

sp

Linear

dp

2

p

2

Bent (angular)

ds

d

2

sp

2

Trigonal planar

0.155

ds

2

3

p

3

Trigonal pyramidal

d

2p

sp

2d

Square planar

p

2d

2

4

sp

3

Tetrahedral

0.225

d

3s

d

4

Tetragonal

pyramidal

sp

3d

Trigonal bipyramidal

0.155

5

d

3sp

6

d

2sp

3

Octahedral

0.414

d

4sp

Trigonal prism

7

One atom above the face

0.592

of an

octahedron,

which

is distorted

chiefly by separating

the atoms at the cor-

ners of this face.

d

4sp

3

Square antiprism (dodec-

0.645

8

ahedral)

Cube

0.732

Formed by adding atoms

0.732

9

beyond

each of the

vertical faces of a right

triangular prism.

12

Cube-octahedron

1.000