Why don't B, C, Si, have ionic forms?
Boron: borates, borides.  $\ce{MgB2}$ is the highest temperature BCS superconductor by a large margin.

Carbon: carbonates, carbides, hexacoordinate carbon in complexes, organolithiums, Grignard reagents, carbenium ions ($\ce{Ph3C+}$).  $\ce{Al4C3}$ hydrolyzes to methane.

Silicon: silicates, aluminosilicates, silicides.  Cook up silica gel in ethylene glycol plus potassium hydroxide (NOT in glass) to get pentacoordinate siliconate, 

http://patentimages.storage.googleapis.com/WO1994020507A1/imgf000014_0001.png

You asked the second half in the Physics Stack.