Reaction of alkaline earth metals with O 2

[anigeo]

reaction of alkaline Earth metals with O₂

i just got in my textbook that Ba,Ca,Sr is kept in paraffin but Mg and Be are not as they form a protective coat of oxide on their surface.i don't get a clue about this .could anyone explain me this?

 

[Borek]

I don't understand what you don't understand - alkaline metals differ, the lower you are in the periodic table, the more reactive they are. Be and Mg are mildly reactive, they can be kept in contact with the air, those below react violently with the air oxygen, so they are kept submerged in an inert liquid.

 

[anigeo]

I don't understand what you don't understand - alkaline metals differ, the lower you are in the periodic table, the more reactive they are. Be and Mg are mildly reactive, they can be kept in contact with the air, those below react violently with the air oxygen, so they are kept submerged in an inert liquid.

what about the coat of oxide on the surface of Mg and Be that prevents them from being attacked by acids.

 

[Borek]

what about the coat of oxide on the surface of Mg and Be that prevents them from being attacked by acids.

Again, I don't understand what you don't understand and I can only repeat, almost word for word, what you wrote. Fresh surface of the Mg and Be reacts quickly with the air oxygen. Produced oxides stick strongly to the surface and are relatively nonreactive, thus they isolate bulk metal below from the further reactions.