Problem 202 - A Complete Resource Book in Chemistry for JEE Main

Question

In silicon dioxide (a) there are double bonds between silicon and oxygen atoms (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 silicon atoms (d) each silicon atom is surrounded by four oxygen atoms and each oxygen atom is bounded to two silicon atoms

Step-by-Step Solution

Answer

(d) Each silicon atom is surrounded by four oxygen atoms and each oxygen atom is bonded to two silicon atoms.

Step 1: Understanding Silicon Dioxide Structure

Silicon dioxide, or SiO₂, is a compound composed of silicon and oxygen. In its most common form, quartz, each silicon atom is covalently bonded to four oxygen atoms, forming a tetrahedral structure. This is a key consideration in determining the correct statement.

Step 2: Analyzing Bonding in SiO₂

In silicon dioxide, each silicon atom forms single covalent bonds with four oxygen atoms. Each oxygen atom is shared between two silicon atoms. This means that there are no double bonds between silicon and oxygen.

Step 3: Evaluating Each Statement

(a) Incorrect. There are no double bonds, only single bonds. (b) Incorrect. Silicon is not bonded directly to another silicon atom in the silica network. (c) Incorrect. Silicon is surrounded by four oxygen atoms, not two. (d) Correct. Each silicon atom is surrounded by four oxygen atoms and each oxygen atom is bonded to two silicon atoms.

Key Concepts

Covalent Bonding

Covalent bonding is a fundamental type of chemical bond where atoms share pairs of electrons. This sharing allows atoms to fill their outer electron shells, achieving greater stability. Silicon dioxide (\( \text{SiO}_2 \) ), commonly known as silica, is an excellent example to study covalent bonding.

• In silica, each silicon atom shares electrons with four oxygen atoms.
• This creates strong single covalent bonds between silicon and oxygen.
• These bonds provide phenomenal stability to the crystal structure of silicon dioxide.

Unlike metals that conduct electricity through free electrons, covalent materials like silicon dioxide do not have such loosely bound electrons, making them excellent insulators. The covalent bonds in silica are key to its hardness and transparency. The robustness of these bonds ensures that silicon dioxide structures are extremely durable, which is why they are commonly used in construction, glassmaking, and even electronics.

Tetrahedral Structure

Silicon dioxide showcases a tetrahedral structure, which is vital to understanding its properties. In 3D terms, a tetrahedron is a pyramid with four triangular faces. In silica, each silicon atom is at the center of a tetrahedron, where it is bonded with four oxygen atoms located at the vertices.

• This arrangement maximizes the distance between bonds, thereby reducing potential energy.
• It imparts a three-dimensional network that extends throughout the crystal.

The tetrahedral structure greatly contributes to the rigidity and spatial arrangement of silicon dioxide. It also influences how SiO₂ interacts with light, accounting for the refraction seen in quartz crystals.

Quartz Form

Quartz is the most common form of silicon dioxide. This crystalline form is responsible for many of its unique properties. Quartz consists of an extensive network of tetrahedrally bonded silicon and oxygen atoms. The orderly pattern of quartz not only gives it a distinct crystal shape but also a high resistance to weathering and chemical reactions.

• Quartz is highly stable at Earth's surface temperatures, making it abundant in geological formations.
• It is found in sand, granite, and a host of other minerals.

The quartz form of SiO₂'s ability to withstand high temperatures makes it invaluable in industrial applications, from glassmaking to high-performance laboratory equipment.

Oxygen and Silicon Bonds

In silicon dioxide, the interplay between silicon and oxygen bonds is crucial. Each silicon atom is bonded to four oxygen atoms, while each oxygen atom connects to two silicon atoms.

• This sharing of oxygen atoms between two silicon atoms maintains the charge balance and stability within the compound.
• This dual connection ensures a continuous network throughout the crystal structure.

These bonds form a robust lattice offering exceptional hardness and stability. By examining these bonds, scientists can better understand physical properties such as rigidity and compressive strength. This bonding arrangement plays a vital role in making silicon dioxide a versatile material across different scientific and industrial fields.