Iodine

Iodine, I₂, reacts with concentrated nitric acid, forming iodic acid [5].

I₂(s) + 10 HNO₃(aq) 2 HIO₃(s) + 10 NO₂(g) + 4 H₂O(g)

Iodine, I₂, does not react with oxygen, O₂, or nitrogen, N₂. It does reat with ozone, O₃, forming the unstable yellow I₄O₉.

Iodine, I₂, reacts with hot aqueous alkali, forming iodate IO₃⁻.

3 I₂(s) + 6 OH⁻(aq) IO₃⁻(aq) + 5 I⁻(aq) + 3 H₂O(l)

Iodine, I₂, reacts with fluorine, F₂, at room temperature, forming iodine(V) fluoride. At 250 °C the product is iodine(VII) fluoride. At -45 °C, suspension in CFCl₃, iodine(III) fluoride is formed.

I₂(s) + 5 F₂(g) 2 IF₅(l) [colourless]
I₂(g) + 7 F₂(g) 2 IF₇(g) [colourless]
I₂(s) + 3 F₂(g) 2 IF₃(s) [yellow]


Iodine, I₂, reacts with bromine, Br₂, forming the very unstable, low melting solid iodine(I) bromide.

I₂(s) + Br₂(l) 2 IBr(s)


Iodine, I₂, reacts with excess chlorine, Cl₂, at -80 °C, forming iodine (III) chloride, I₂Cl₆ (note that the formula is not ICl₃ as one would expect). At room temperature, in the presence of water, iodic acid is formed.

I₂(s) + 3 Cl₂(l) I₂Cl₆(s) [yellow]
I₂(aq) + 6 H₂O(l) + 5 Cl₂(g) 2 HIO₃(aq) + 10 HCl(g)

Hydrogen reacts with I₂ forming hydrogen iodide. The reaction is slow at room temperature, and increases in speed with increasing temperatures [5].

H₂(g) + Br₂(g) 2 HBr(g)

Solid Cd does not react with I₂(g), but will react with I₂(aq). In gas phase Cd and I₂ will react forming CdI₂. At high temperature and pressure (e.g. a steel bomb) equivalent Cd and I₂ will react forming CdI [4].

Cd(s) + I₂(aq) Cd²⁺(aq) + 2 I⁻(aq)
Cd(g) + I₂(g) CdI₂(g)
2 Cd(g) + I₂(g) 2 CdI(g)


Manganese with oxidation steps >2 will be reduced to Mn(II) by I⁻ under acidic conditions under the formation of I₂, e.g.

MnO₂(s) + 2 I⁻(aq) + 4 H⁺(aq) Mn²⁺(aq) + I₂(aq) + 2 H₂O(l)

Iodine, I₂, reacts with water, forming hypoiodite, IO⁻.

I₂(aq) + H₂O(l) IO⁻ + 2 H⁺(aq) + I⁻(aq)