Reaction of iridium with acids
Iridium metal is resistant to acids, including aqua regia.
Reaction of iridium with air
Iridium react with O2 when heated.
Ir(s) + O2(g) IrO2(s) [black]
Reaction of iridium with halogens
Iridium metal reacts with fluorine forming iridium(VI) fluoride, IrF6, and a minor amount of iridium(III) fluoride, IrF3. Carefully heated, iridium(VI) fluoride will form the yellow tetrameric structure [IrF5]4.
3 Ir(s) + 6 F2(g) IrF6(s) [yellow] + 2 IrF3(s) [black]
IrF6(s) [IrF5]4 [yellow]
Iridium reacts with Cl2, Br2 and I2, under dry conditions, forming the corresponding iridium(III) halides
2 Ir(s) + 3 Cl2(g) 2 IrCl3(s) [red]
2 Ir(s) + 3 Br2(g) 2 IrBr3(s) [red-brown]
2 Ir(s) + 4 I2(g) 2 IrI3(s) [dark brown]
Reaction of iridium with water
Iridium does not react with water under normal conditions.