Molecules may also have a mixture of bonding and non-bonding electron pair domains at the central atom.
The arrangement of electron pair domains and shape descriptors are shown below for the molecules of type AXmEn where
The arrangement of electron pair domains about the central atom depends on the total number of domains.
The shape descriptor depends on the location of outer atoms with respect to the central atom.
The shape descriptor depends on the location of outer atoms with respect to the central atom.
The arrangement of electron pair domains and shape descriptors are shown below for the molecules of type AXmEn where
X is an atom bonded to central atom A
E is a non-bonding electron pair at central atom A
the sum m+n is either three or four.
The diagrams show the three-dimensional arrangement of bonds.
Those atoms joined to the central atom by a
E is a non-bonding electron pair at central atom A
the sum m+n is either three or four.
| AXmEn where m+n equals 3 | |
| AX3 | AX2E |
| electron pair domain arrangement | |
| trigonal planar for both | |
 | |
| shape | |
| trigonal planar | bent |
 |  |
| AXmEn where m+n equals 4 | ||
| AX4 | AX3E | AX2E2 |
| electron pair domain arrangement | ||
| tetrahedral for all | ||
 | | |
| shape | ||
| tetrahedral shape | trigonal pyramid | bent |
 |  |  |
The diagrams show the three-dimensional arrangement of bonds.
Those atoms joined to the central atom by a
solid line (—) are in the plane of the screen.
solid wedge (
) point to atoms in front of the plane of the screen.
hashed wedge (
) point to atoms behind the plane of the screen.
solid wedge (
) point to atoms in front of the plane of the screen.hashed wedge (
) point to atoms behind the plane of the screen.