Question

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?

Short answer

Silicon (Si) is a covalent-network solid because it has a tetrahedral structure with each Si atom covalently bonded to four other Si atoms, similar to diamond. This results in a strong and rigid structure due to the large number of covalent bonds.

Step-by-step solution

Analyze Silicon's properties

Silicon, like diamond, is a solid at room temperature and has a tetrahedral (four bonded atoms) structure. This means that each Si atom is covalently bonded to four other Si atoms. Covalent bonds are formed when atoms share electrons, which is the case for Silicon.

Compare the possible solid types

Let's quickly go over the four types of solids and their main characteristics: 1. Molecular solids: Formed by atoms held together by weak intermolecular forces (e.g., van der Waals forces). Example: Ice 2. Metallic solids: Formed by metal atoms that share a "sea" of free-moving electrons. Example: Iron 3. Ionic solids: Formed by positive and negative ions held together by their electrostatic attraction. Example: Sodium chloride 4. Covalent-network solids: Formed by atoms that are bonded together by a large number of covalent bonds. Example: Diamond

Identify Silicon as a covalent-network solid

Based on its tetrahedral structure and the fact that it shares the same structure as diamond, we can deduce that Silicon is a covalent-network solid. This is because each Si atom is covalently bonded to four other Si atoms in a three-dimensional network, similar to the structure of diamond. In such a solid, the large number of covalent bonds results in a strong and rigid structure.

Key concepts

Silicon Properties

Silicon is an extraordinary element widely recognized for its role as the backbone of modern electronics. Its properties are fascinating—in its purest form, silicon is a shiny, metallic-looking solid. This element occupies a place in the periodic table as a metalloid, meaning it holds properties of both metals and non-metals.

Unique for its ability to conduct electricity under certain conditions, silicon becomes the platform upon which the semiconductor industry has built an empire. Silicon crystals are arranged in a rigid lattice pattern, sharing electrons with four neighboring atoms in what's known as a tetrahedral configuration. This structure not only gives silicon its signature strength but also enables it to withstand high temperatures and pressures. A noteworthy property of silicon is its relative abundance on Earth, which makes it accessible for widespread use in technologies such as solar panels and microprocessors.

Types of Solids

Understanding the fundamental types of solids is crucial for comprehending the complex world of materials science. So, let's simplify this by categorizing solids into four primary types: molecular, metallic, ionic, and covalent-network.

• Molecular solids: These solids are usually composed of non-metal atoms. They're held together by relatively weak forces like London dispersion forces or hydrogen bonds. Water ice and dry ice (frozen carbon dioxide) are classic examples.
• Metallic solids: Metals form these solids, where atoms are surrounded by a cloud of electrons that move freely, attributing to the conductivity and malleability of metals such as copper and gold.
• Ionic solids: Composed of positively charged ions and negatively charged ions, which are attracted to each other through electrostatic forces. Ordinary table salt (sodium chloride) is a familiar example of an ionic solid.
• Covalent-network solids: Atoms in these solids are interconnected by covalent bonds throughout the material, creating a rigid and sturdy structure. Diamond, quartz, and indeed silicon are prime examples of this solid type.

Each type of solid offers distinctive physical characteristics—molecular solids are generally soft and have low melting points, metallic solids are conductive and ductile, ionic solids exhibit high melting points and are often soluble in water, while covalent-network solids are hard and have high melting points, showcasing the diversity within the realm of solid-state chemistry.

Covalent Bonds

Covalent bonds are the glue that holds together many of the world's most durable and interesting materials. These chemical bonds form when two atoms share one or more pairs of electrons, establishing a strong connection that greatly impacts the material's properties. The strength of a covalent bond is one of its most significant attributes, engendering substances with excellent stability and resilience.

Covalent bonds are not only responsible for the formation of simple molecules like water (H2O) but also for more complex structures like the long chains of carbon atoms found in polymers. In covalent-network solids, these bonds create a three-dimensional network that contributes to their high melting and boiling points, as well as their hardness. The shared electrons provide a balance that affords these materials with neither purely ionic nor metallic characteristics but a mix that creates insulators, semiconductors, and superconductors, thus driving innovation across multiple technology sectors.