This is a picture showing how silicium atoms share electrons together in the form of a silicium crystal.

 

 

The silicon atoms are not arranged in squares like that, nor in a single flat layer.

http://en.wikipedia.org/wiki/File:Silicon-unit-cell-3D-balls.png

And this representation of chemical bonds is wrong and misleading:

- Orbitals are not orbits

- The eight electrons together make little sense

- Valence electrons are shared across the whole crystal, not just neighbour atoms