3D cubic cluster with 24 bonds = 4*6

(Si3N4)2 cluster

With 4 bonds

With 3 bonds

Molecule

(Si3N4)2

[13]

(Al4C3)2

[13]

(As3O4)2

Charged [12]

(As4O3)2 [12] (Sb4Sn3)2 [15]

Neutral

Grey 4 bonds for: silicon, carbon, oxigen or charged arsenic

Orange 3 bonds for: nitrogen, aluminum, arsenic or charged oxigen