Question

Silicon is the fundamental component of integrated circuits. Si has the same structure as diamond. (a) Is Si a molecular, metallic, ionic, or covalent- network solid? (b) Silicon readily reacts to form silicon dioxide, \(\mathrm{SiO}_{2}\) , which is quite hard and is insoluble in water. Is \(\mathrm{SiO}_{2}\) most likely a molecular, metallic, ionic, or covalent- network solid?

Short answer

(a) Silicon (Si) is a covalent-network solid. (b) Silicon dioxide (SiO2) is most likely a covalent-network solid.

Step-by-step solution

Silicon (Si) has the same structure as diamond, which means it has a covalent-network solid structure. In a covalent-network solid, atoms are held together by covalent bonds in an extensive three-dimensional network. Since Si has four valence electrons and bonds with four other Si atoms, it forms a covalent-network solid. So, the answer for part (a) is: Silicon (Si) is a covalent-network solid. #Step 2: Determine the type of solid for Silicon dioxide (SiO2)#

Silicon dioxide (SiO2) is formed when Silicon reacts with Oxygen. Oxygen has six valence electrons and tends to form two covalent bonds to complete its octet. While Silicon has four valence electrons and can form four covalent bonds. When they react, each Silicon atom bonds with two Oxygen atoms, and each Oxygen atom bonds with two Silicon atoms in a three-dimensional lattice structure. This kind of bonding is characteristic of a covalent-network solid. The fact that SiO2 is hard and insoluble in water also indicates that it is a covalent-network solid. So, the answer for part (b) is: Silicon dioxide (SiO2) is most likely a covalent-network solid.

Key concepts

Understanding Silicon Structure

Silicon, often symbolized as Si, is a fascinating element that shares its structural properties with diamond. This means that silicon forms a covalent-network solid. In this type of solid, atoms are connected in an extensive, three-dimensional network by covalent bonds. Unlike metals or ionic compounds that have conductive or easily breakable lattice structures, the network in covalent solids is quite rigid. Solid silicon is built from each Si atom bonding to four neighboring Si atoms. This connection happens because every silicon atom has four valence electrons, which are utilized to form covalent bonds. These strong, directional bonds are the reason behind its strong, sturdy nature and the mechanism that makes it such a crucial material for electronics like integrated circuits. The three-dimensional structure minimizes spaces within the lattice, limiting movement of electrons, which contributes to silicon's semi-conducting nature.

The Role of Silicon Dioxide

Silicon dioxide, or SiO extsubscript{2}, is another important compound of silicon. It's found abundantly in nature, often recognized as sand or quartz. The formation of SiO extsubscript{2} occurs when silicon atoms react with oxygen atoms. Silicon dioxide adopts a covalent-network structure, similar to pure silicon, but with significant differences. Here, each silicon atom shares covalent bonds with oxygen atoms. Specifically, each silicon forms bonds with two oxygen atoms, and each oxygen bonds to two silicon atoms, creating a robust network.
This resulting structure forms a three-dimensional lattice, which is tough and not easily broken. Due to these covalent connections, silicon dioxide is incredibly hard and insoluble in water. Unlike simple molecular compounds, where atoms or molecules are easily separated in solution, the extensive lattice of SiO extsubscript{2} stays intact, confirming its identity as a covalent-network solid.

Exploring Chemical Bonding

Chemical bonding plays a crucial role in determining the properties and structures of materials like silicon and silicon dioxide. Covalent bonds, specifically, are formed when atoms share pairs of electrons, creating a strong linkage between them. In covalent-network solids, such as silicon and SiO extsubscript{2}, these shared electrons create an extensive lattice.

• Single Bonds: In silicon, each Si atom forms a single covalent bond with four other silicon atoms. This results in a very stable and strong lattice.
• Double Bonds: In SiO extsubscript{2}, there are no typical double bonds, but each silicon-oxygen connection achieves a similar bond strength to a single bond, causing a robust three-dimensional network.

The outcome of such bonding is significant in the characteristics of the materials. The strong covalent bonds result in a high melting point, hardness, and electrical semi-conductivity for silicon. Meanwhile, the immense stability and insolubility of SiO extsubscript{2} demonstrate how covalent-network bonding can lead to highly durable and non-reactive materials.