Chapter 9 Memory Bank

2 electron domains

linear; sp; 180°

3 electron domains

trigonal planar; sp^2; 120°

4 electron domains

tetrahedral; sp^3; 109.5°

5 electron domains

trigonal bipyramidal; sp^3d; 90°, 120°, and 180°

6 electron domains

octahedral; sp^3d^2; 90° and 180°

single bond domain count

1 domain

double bond domain count

1 domain

triple bond domain count

1 domain

lone pair on central atom

1 domain

4 domains with 0 lone pairs

tetrahedral

4 domains with 1 lone pair

trigonal pyramidal

4 domains with 2 lone pairs

bent

5 domains with 0 lone pairs

trigonal bipyramidal

5 domains with 1 lone pair

seesaw

5 domains with 2 lone pairs

T-shaped

5 domains with 3 lone pairs

linear

6 domains with 0 lone pairs

octahedral

6 domains with 1 lone pair

square pyramidal

6 domains with 2 lone pairs

square planar

polarity test step 1

determine whether the bonds are polar

polarity test step 2

determine the molecular shape

polarity test step 3

determine whether the bond dipoles cancel by symmetry

symmetry and polarity rule

a symmetric molecule with identical outer atoms is often nonpolar; an asymmetric molecule is often polar

single bond sigma/pi count

1 sigma

double bond sigma/pi count

1 sigma + 1 pi

triple bond sigma/pi count

1 sigma + 2 pi

sigma-bond counting rule

count one sigma for every directly connected pair of atoms