Arsenic - ₃₃As: reactions of elements

Reaction of arsenic with air

Arsenic is stable in dry air, but the surface oxidizes slowly in moist air to give a bronze tarnish and finally a black covering to the element. When heated in air, arsenic ignites "arsenic trioxide" - actually tetraarsenic hexaoxide, As₄O₆. This is accompanied by phosphorescence under some conditions. When heated in oxygen, arsenic ignites in oxygen to form "arsenic pentoxide" - actually tetraarsenic decaoxide, As₄O₁₀, and As₄O₆.

4As(s) + 5O₂(g) → As₄O₁₀(s)

4As(s) + 3O₂(g) → As₄O₆(s)

Reaction of arsenic with water

Arsenic does not react with water in the absence of air under normal conditions.

Reaction of arsenic with the halogens

Arsenic reacts with fluorine, F₂, to form the gas pentafluoride arsenic(V) fluoride.

2As(s) + 5F₂(g) → 2 AsF₅(g) [colourless]

Arsenic reacts under controlled conditions with the halogens fluorine, F₂, chlorine, Cl₂, bromine, Br₂, and iodine, I₂, to form the respective trihalides arsenic(III) fluoride, AsF₃, arsenic(III) chloride, AsCl₃, arsenic(III) bromide, AsBr₃, and arsenic(III) iodide, AsI₃.

2As(s) + 3F₂(g) → 2AsF₃(l) [colourless]

2As(s) + 3Cl₂(g) → 2AsCl₃(l) [colourless]

2As(s) + 3Br₂(g) → 2AsBr₃(s) [pale yellow]

2As(s) + 3I₂(g) → 2AsI₃(s) [red]

Reaction of arsenic with acids

Reaction of arsenic with bases