[Shadow]

Last year IChO question. "One molecule of nitrogen falls on x carbon atoms". How much is x? This should be concluded from the picture. Two carbon atoms make one hexagon, but I don't know anything more.

[Radu]

  Hi, one of  Moscow's trickest problem ).
        The idea is that a nitrogen molecule falls in one hexagone. Every carbon atom is part of three different hexagones. So, one can conclude that the contribution of one carbon atom to one hexagone is 1/3. There are 6 carbon atoms in a hexagone, so 6*1/3=2 carbon atoms for every absorbed nitrogen molecule.

     Hoope we'll see in Vietnam, if you're a student ^^.

[Shadow]

The answer is 6. How to explain that?

[Radu]

  Ah, I see. Well, apparently there are no two adjacent hexagones ( edge-sharing or corner-sharing)  which absorb nitrogen molecules ( repulsions between pi orbitals of N₂, maybe). So there are 6 carbon atoms for every absorbed N₂. ( every C is a part of a single hexagon capable of absorbing nitrogen, in other words).

[Shadow]

I appreciate your help. Yes, I am preparing for the qualification rounds to pass to Vietnam. Were you in Moscow?

[Radu]

  Yes, I was in Russia. Can't wait for the preparatories. :-s Wonder what advanced topics they'll include.