Carbon

Carbon has a weakly acidic oxide.  The  last p+  added to the configuration attracts the orbiting p+ and the two binds together as they are similar charges moving in the same direction.  This is why carbonic acid is a stronger acid then boric acid.

The carbon atom makes four bonds with neighboring atoms, has no free electron and can form a very structured and hard lattice.

In 3D all bonds are at equal angles.