Boron: reactions of elements
Reaction of boron with air
The behaviour of boron to air depends upon the crystallinity of the sample, temperature, particle size, and purity. By and large, boron does not react with air at room temperature. At higher temperatures, boron does burn to form boron (III) oxide, B2O3.
4B + 3O2(g) → 2B2O3(s)
Reaction of boron with water
Boron does not react with water under normal conditions.
Reaction of boron with the halogens
Boron reacts vigorously with the halogens fluorine, F2, chlorine, Cl2, bromine, Br2 to to form the trihalides boron(III) fluoride, BF3, boron(III) chloride, BCl3, and boron(III) bromide, BBr3 respectively.
2B(s) + 3F2(g) → 2BF3(g)
2B(s) + 3Cl2(g) → 2BCl3(g)
2B(s) + 3Br2(g) → 2BF3(l)
Reaction of boron with acids
Crystalline boron does not react with boiling hydrochloric acid, HCl, or boiling hydrofluoric acid, HF. Powdered boron oxidizes slowly when treated with concentrated nitric acid, HNO3.