Question

In silicon dioxide: (a) there are double bonds between silicon and oxygenatoms. (b) silicon is bonded to two silicon atoms. (c) each silicon atom is surrounded by two oxygen atoms and each oxygen atom is bonded to two sil con atoms. (d) each silicon atom is surrounded by four oxygen atoms and each oxygen atom is bounded to two silicon atoms.

Short answer

The correct statement is (d): each silicon atom is surrounded by four oxygen atoms, and each oxygen atom is bonded to two silicon atoms.

Step-by-step solution

Identify the Molecular Structure of Silicon Dioxide

Silicon dioxide (SiO₂) is commonly known as silica and has a three-dimensional network structure. To determine the bond arrangement in this compound, let's first consider the typical valency of the involved elements. Silicon usually forms four bonds, and oxygen typically forms two bonds.

Analyze Possible Bonding Scenarios

Consider the descriptions provided: - A double bond configuration is rare for silicon in its oxide form, as silicon prefers tetrahedral geometry. - Silicon atoms are usually bonded to oxygen rather than directly to other silicon atoms, opposing the notion of direct Si-Si bonds. - An arrangement where each silicon atom is surrounded by two or four oxygen atoms is common, but structural knowledge and valency favor four oxygen atoms per silicon.

Evaluate Each Given Statement

Let's evaluate: (a) Silicon forming double bonds with oxygen is unlikely due to preference for tetrahedral coordination. (b) Silicon bonded to two silicon atoms conflicts with the network structure and tetrahedral coordination. (c) Silicon surrounded by two oxygen atoms does not satisfy its tetrahedral requirement. (d) Each silicon atom surrounded by four oxygen atoms fits with the tetrahedral requirement, while each oxygen bonded to two silicon atoms ensures oxygen's valency is met.

Determine the Correct Statement

Based on the evaluation, the crystal structure of silicon dioxide involves each silicon atom tetrahedrally coordinated by four oxygen atoms, and each oxygen atom forming bridges between two silicon atoms, aligning with statement (d).

Key concepts

Tetrahedral Geometry

Tetrahedral geometry is a term used to describe the arrangement of atoms in a molecule where a central atom is surrounded symmetrically by four other atoms or groups. In silicon dioxide (SiO₂), each silicon atom is at the center of a tetrahedron with oxygen atoms at the corners. This type of arrangement arises because silicon, based on its valency and electron configuration, tends to form four bonds.
Silicon's tetrahedral shape is not just a theoretical idea; it has real chemical advantages. This geometry optimizes the spatial distribution of electrons, reducing repulsion between bonded electrons and giving the molecule better stability.
In the context of silicon dioxide, this tetrahedral bonding ensures that each silicon atom is surrounded by four oxygen atoms. This arrangement is a defining aspect of silica's stable, three-dimensional structure.

Oxygen Valency

Valency is a fundamental concept in chemistry, referring to the ability of an atom to combine with other atoms, dictated by the number of bonds it forms. Oxygen has a valency of two, meaning it typically forms two bonds to achieve stability by gaining electrons to fill its outer electron shell.
In silicon dioxide, each oxygen atom forms bonds according to its valency. It bonds with two silicon atoms, effectively "bridging" between them. This arrangement not only satisfies oxygen’s need for two bonds but also supports the tetrahedral geometry around each silicon atom.
By understanding the valency of oxygen, we can better appreciate why silicon dioxide forms its unique network structure, where oxygen atoms connect silicon atoms together, maintaining both structural integrity and chemical stability.

Silicon-Oxygen Bonding

The bonding between silicon and oxygen in silicon dioxide is crucial for its structure and properties. Each silicon atom forms covalent bonds with oxygen atoms. Covalent bonds arise when atoms share pairs of electrons, leading to stable molecules.
In SiO₂, the bonds are strong because of the stable covalent interactions between silicon and oxygen, which also involves overlapping atomic orbitals. The bonds not only play a role in maintaining the tetrahedral geometry but also ensure the robustness of the entire silica network.
Silicon and oxygen prefer a single bond in this compound, contrary to other potential types like double bonds. This preference allows silicon to maximize its coordination number, forming a strong and extensive network solid that makes silica resilient to heat and pressure.

Network Structure

Silicon dioxide features a fascinating network structure, characteristic of many of its physical properties. This network solid is formed by continuous covalent bonding, creating a three-dimensional lattice.
Each silicon atom bonds tetrahedrally with four oxygen atoms, while each oxygen forms bonds with two silicon atoms. This structure creates a repeating pattern that extends throughout the material, resulting in a highly stable and rigid network.
Such a network structure is responsible for the hardness of substances like quartz, a form of crystalline silica. The robustness of this lattice contributes significantly to its durability and resistance to weathering, making silica one of the most abundant and resilient minerals on Earth.

• Ensures structural integrity
• Contributes to hardness and durability
• Provides thermal and chemical stability