Reaction of palladium with air
Palladium can be brought to react with oxygen, O2, by heating the palladium.
2 Pd(s) + O2(g) PdO(s) [black]
Reaction of palladium with halogens
Palladium will react with F2, Cl2 and Br2 forming palladium halides.
For fluorine, at mixture of Pd(II) and Pd(IV) is formed, and not Pd(III) as one could be led to believe:
2 Pd(s) + 3 F2(g) [Pd(II)Pd(IV)F6](s)
For chlorine, Pd(II)chloride is formed. Depending on the reaction conditions, two different forms are produced.
Pd(s) + Cl2(g) PdCl2(s)
For bromine, Pd(II)bromide is formed.
Pd(s) + Br2(g) PdBr2(s) [red-black]