Problem: Silicon is the fundamental component of integrated circuits. Si has the same structure as diamond.Is Si a molecular, metallic, ionic, or covalent-network solid?

We’re being asked to determine if Si is molecular, metallic, ionic or covalent-network solid.

There are two main categories which are crystalline and amorphous solids. Crystalline solids are well ordered at the atomic level and amorphous solids are disordered. There are four types of crystalline solids:

• Ionic crystals – The ionic crystal structure consists of alternating positively-charged cations and negatively-charged anions. The ions may be monoatomic or polyatomic.
• Metallic crystal - Metallic crystals consist of metal cations surrounded by a "sea" of mobile valence electrons. These electrons, also referred to as delocalized electrons, do not belong to any one atom, but are capable of moving through the entire crystal.