Reaction of molybdenum with air
At room temperature, molybdenum does not react with air or oxygen, O2. At elevated temperatures (red heat), the trioxide molybdenum(VI) oxide, MoO3, is formd.
2Mo(s) + 3O2(g) → 2MoO3(s)
Reaction of molybdenum with water
At room temperature, molybdenum does not react with water.
Reaction of molybdenum with the halogens
Molybdenum reacts directly with fluorine, F2, at room temperature to form molybdenum(VI) fluoride, MoF6. The conditions are much milder than those required for chromium (immediately above molybdenum in the periodic table).
Mo(s) + 3F2(g) → MoF6(l) [colourless]
Under carefully controlled conditions, molybdenum(V) fluoride, MoF5, is formed in the reaction between molybdenum metal and chlorine, Cl2.
2Mo(s) + 5Cl2(g) → 2MoCl5(s) [black]