- Point group
- D∞h — A linear molecule with a centre of inversion: the C∞ axis, the planes containing it, a perpendicular mirror plane and an infinite number of perpendicular C2 axes.
- Order
- ∞
- Operations
- E, 2C∞, ∞σᵥ, i, 2S∞, ∞C₂
- Shape
- Linear
- Atoms
- 3 (I × 3)
Symmetry elements of I₃⁻
- C∞ — the molecular axis: any rotation leaves the molecule unchanged
- σᵥ (one of ∞) — any plane containing the axis
- σᵥ (another) — any plane containing the axis
- i — centre of inversion
- σh — perpendicular to the axis, through the centre
- C₂ (one of ∞) — any line through the centre perpendicular to the axis
- C₂ (another) — same, at right angles
- S∞ — any rotation about the axis, then reflect in σh
Structure
- I–I 2.92 Å
- I–I–I 180°
- Three lone pairs on the central I (AX₂E₃)
