[Rutherford]

Write the formulas of the 3 anions of polyoxosilicate (not sure if I wrote well,but it doesn't matter I think) that are on the map. Legend:
1-Si atoms
2-O atoms bounded to two Si atoms
3-O atoms bounded to one Si atom

I don't understand this.

[AWK]

http://en.wikipedia.org/wiki/Silicates

[Rutherford]

"Si occupies a tetrahedral environment, being surrounded by 4 oxygen centres."
Using this for the first example, the building block are SiO₄, and I calculated the number of O atoms as if it was a cubic crystal unit cell (2 that are in one unit, and 2 are share between 2 units) and I got 3, so it is SiO₃^2-.
Now, the example B), the building block (units) are the hexagons 2+4/2=4 Si atoms, now to determine the number of O atoms is 4+2/2+4+4/2=11, it is Si₄O₁₁^6-.
Example C), 6*1/3=2 Si and 6*1/2+6*1/3=5 O, it is Si₂O₅^2-.
I didn't have the idea to solve this one for almost a whole year, and now your link made me realize that it is the same principle like the one for the cubic cells. I am satisfied now  . Thanks for the link.