Shapes of Molecules

Adapted from Silberberg, section 10.3, p. 374-384. (References)

"Things" on central atom (1)
Bonds	Lone Pairs	AXmEn (2)	Shape	Bond Angles (3)	"Usual" Polarity  (4)	Hybrid- ization	Appearance
2	0	AX2	linear	180°	nonpolar	sp
3	0	AX3	trigonal planar	120°	nonpolar	sp2
2	1	AX2E	bent, nonlinear	<120°	polar	sp2
4	0	AX4	tetrahedral	109.5°	nonpolar	sp3
3	1	AX3E	trigonal pyramidal	<109.5°	polar	sp3
2	2	AX2E2	bent, nonlinear	<109.5°	polar	sp3
5	0	AX5	trigonal bipyramidal	120° eq 90° ax	nonpolar	sp3d
4	1	AX4E	unsymmetrical tetrahedron, seesaw	<120° eq <90° ax	polar	sp3d
3	2	AX3E2	T-shaped	90°	polar	sp3d
2	3	AX2E3	linear	180°	nonpolar	sp3d
6	0	AX6	octahedral	90°	nonpolar	sp3d2
5	1	AX5E	square pyramidal	<90°	polar	sp3d2
4	2	AX4E2	square planar	90°	nonpolar	sp3d2

1   "Things" include bonds and lone pairs. Remember, a multiple bond counts as one "thing"!

2   X = surrounding atom; E = lone pairs

3   Lone pairs take up more room than covalent bonds, causing the remaining covalent bonds on the central atom to be "squashed" together slightly.

4   This is the polarity when all of the atoms connected to the central atom are identical (AX_m). If more than one type of atom is connected to the central atom, you will have to look at the overall shape of the molecule and the relative polarity of each bond to determine the polarity.

References

Martin S. Silberberg, Chemistry:  The Molecular Nature of Matter and Change, 2nd ed.  Boston:  McGraw-Hill, 2000, p. 374-384.