Years From Now: MOLECULAR GEOMETRY

Molecular geometry is the three-dimensional arrangement of the atoms that constitute a molecule. It determines several properties of a substance including its reactivity, polarity, phase of matter, color, magnetism, and biological activity. The angles between bonds that an atom forms depend only weakly on the rest of molecule, i.e. they can be understood as approximately local and hence transferable properties.

The bond angles in the table below are ideal angles from the simple VSEPR theory, followed by the actual angle for the example given in the following column where this differs. For many cases, such as trigonal pyramidal and bent, the actual angle for the example differs from the ideal angle, but all examples differ by different amounts. For example, the angle in H₂S (92°) differs from the tetrahedral angle by much more than the angle for H₂O (104.5°) does.

Bonding electron pairs	Lone pairs	Electron domains (Steric #)	Shape	Ideal bond angle (example's bond angle)	Example
2	0	2	linear	180°	CO₂
3	0	3	trigonal planar	120°	BF₃
2	1	3	bent	120° (119°)	SO₂
4	0	4	tetrahedral	109.5°	CH₄
3	1	4	trigonal pyramidal	107°	NH₃
2	2	4	bent	109.5° (104.5°)	H₂O
5	0	5	trigonal bipyramidal	90°, 120°, 180°	PCl₅
4	1	5	seesaw	180°, 120°, 90° (173.1°, 101.6°)	SF₄
3	2	5	T-shaped	90°, 180° (87.5°, < 180°)	ClF₃
2	3	5	linear	180°	XeF₂
6	0	6	octahedral	90°, 180°	SF₆
5	1	6	square pyramidal	90° (84.8°), 180°	BrF₅
4	2	6	square planar	90°, 180°	XeF₄
7	0	7	pentagonal bipyramidal	90°, 72°, 180°	IF₇
6	1	7	pentagonal pyramidal	72°, 90°, 144°	XeOF₅⁻
5	2	7	planar pentagonal	72°, 144°	XeF₅⁻
8	0	8	square antiprismatic		XeF₈²⁻
9	0	9	tricapped trigonal prismatic		ReH₉²⁻