Question

Silicones have the general formula (1) \(\mathrm{SiO}_{4}^{-4}\) (2) \(\mathrm{Si}_{2} \mathrm{O}_{7}^{6-}\) (3) \(\left(\mathrm{R}_{2} \mathrm{SiO}\right)_{n}\) (4) \(\left(\mathrm{Si}_{2} \mathrm{O}_{3}\right)_{n}^{2 n}\)

Short answer

(R2SiO)n

Step-by-step solution

- Understand the Question

Identify the general formula of silicones from the given options. Silicones are a group of synthetic polymers that include silicon, oxygen, carbon, and hydrogen. Focus on understanding the structure of silicones.

- Analyze the Options

Evaluate each provided formula: 1. \(\text{SiO}_{4}^{-4}\): Typically represents silicate, not silicone.2. \(\text{Si}_{2} \text{O}_{7}^{6-}\): Indicates a different type of silicate structure.3. \(\text{(R}_{2} \text{SiO)}_{n}\): Fits the general structure of silicones, where R represents organic groups and the polymer chain repeats.4. \(\text{(Si}_{2} \text{O}_{3}\text{)}_{n}^{2n}\): Doesn't conform to the typical silicone polymer structure.

- Identify the Correct Formula

Based on the analysis in Step 2, \(\text{(R}_{2} \text{SiO)}_{n}\) is identified as the general formula for silicones. This is because silicones are characterized by repeating units of \(\text{R}_{2} \text{SiO}\), where R is an organic group.

Key concepts

Silicone structure

Silicones are unique polymers that primarily consist of silicon, oxygen, carbon, and hydrogen. They feature a backbone made up of alternating silicon and oxygen atoms. This backbone structure is written as \((R_2SiO)_n\), where R represents organic groups like methyl, ethyl, or phenyl. The flexibility of these organic groups allows silicones to exhibit a wide variety of properties. For instance, when R is a methyl group, the silicone will have different characteristics compared to when R is a phenyl group.

Polymer chemistry

Polymer chemistry is the science of polymers, which are large molecules composed of repeating subunits. In the case of silicones, these repeating subunits are \((R_2SiO)_n\). Understanding polymer chemistry helps us comprehend how individual units link together to form long chains, which impacts the properties of the material.
Different arrangements and types of organic groups (R) can lead to varied physical properties such as thermal stability, flexibility, and permeability, making silicones incredibly versatile.
One key aspect is the method of polymerization. Silicones are typically synthesized via a process called 'condensation polymerization,' where monomers react, eliminating small molecules like water to form the polymer.

Silicones in materials science

Silicones play a critical role in materials science because of their unique properties. They are highly resistant to heat, chemicals, and weathering. This makes them ideal for numerous applications ranging from medical devices to household products.
Some common uses of silicones include:

• Sealants and adhesives due to their flexibility and strong bonding capabilities.
• Medical implants and tubing, as they are biocompatible and can withstand sterilization.
• Personal care products like shampoos and conditioners, providing a smooth, silky feel.
• Electrical insulation materials, thanks to their excellent dielectric properties.

Silicones' versatility stems from their stable silicon-oxygen bonds, which do not break down easily, thus allowing them to perform under extreme conditions.