Difference Between Silicon and Silica

Main Difference – Silicon vs Silica

Silicon and silica are two terms often used in inorganic chemistry. Silicon is the second most abundant element on the earth, second only to oxygen. Thus, it is very important to know the difference between silicon and silica. The main difference between silicon and silica is that silicon is an element whereas silica is a compound.

Key Areas Covered

1. What is Silicon
      – Definition, Properties, Uses
2. What is Silica
      – Definition, Properties, Uses
3. What is the difference between Silicon and Silica
     – Comparison of Key Differences

Key Terms: Inorganic Chemistry, Oxygen, Polymorphs, Quartz, Semiconductor, Silica, Silicon, Silicones

What is Silicon

Silicon is an element found in earth crust abundantly. In the periodic table, silicon is a member of group 14 and is categorized as a semi-metal or a metalloid. This is because silicon show some properties of both metals and non-metals.

The atomic number of silicon is 14, and Silicon is positioned in p-block. The electron configuration of silicon is [Ne]3s²3p². Since there are only two electrons in p orbitals of silicon, it can provide space for four more incoming electrons. Therefore, silicon can form maximum of four covalent bonds. The melting point of silicon is about 1414⁰C. Silicon has three stable isotopes; ²⁸Si, ²⁹Si, and ³⁰Si.

Figure 1: Silicon Metalloid

Silicon is a semiconductor. It has so many important applications in electronic industry since it is a good conductor of electricity. Silicon is also used in the synthesis of polymers called silicones. Silicon does not occur as a free element in nature. It always occurs as a mineral with a combination of other elements.

What is Silica

Silica is a compound made out of silicon and oxygen atoms. Silica is the name given for silicon dioxide. The molecular formula of silica is SiO₂. Therefore, silica is made out of two most abundant elements on earth. Silica is found as quartz in nature. Silica is also the major constituent of sand.

Under normal temperature and pressure, silica is a solid. Pure silica is a colorless crystalline compound having a high melting point. The melting point of silica is about 1713^oC. Molar mass of silica is about 60 g/mol. Silica is obtained mostly by mining of quartz.

Although silica is called silicon dioxide, the crystalline structure of silica shows that silicon atom is surrounded by four oxygen atoms attached through single covalent bonds. This is because this tetrahedral structure is more stable.

Silica structure is a stable structure, but it is attacked by hydrofluoric acid (HF) to form hexafluorosilicate acid. This reaction is given below.

SiO₂  +       6HF   →     H₂SiF₆         +       2H₂O

Silica is used in the production of glass. Silica beads are also used in chromatographic applications. 

Figure 2: Silica Beads

Silica occurs in a number of crystalline forms. These forms are called polymorphs. Examples for these polymorphs include α-quartz, β-quartz, coesite, etc.

Difference Between Silicon and Silica

Definition

Silicon: Silicon is an element found in the earth crust.

Silica: Silica is a compound made out of silicon and oxygen atoms.

Composition

Silicon: Silicon is a single element.

Silica: Silica is composed of silicon and oxygen atoms.

Melting Point

Silicon: Melting point of silicon is about 1414⁰C.

Silica: Melting point of silica is about 1713⁰C.

Electrical Conductance

Silicon: Silicon is a semiconductor which can conduct electricity.

Silica: Silica is not capable of conducting electricity.

Occurrence

Silicon: Silicon does not occur alone in nature.

Silica: Silica can occur as a pure compound.

Crystal Structure

Silicon: The crystal structure of silicon is brittle.

Silica: The crystal structure of silica is very hard.

Conclusion

Both silicon and silica contains silicon atoms. But silica is different from silicon due to their structures and properties. The main difference between silicon and silica is that silicon is an element whereas silica is a compound.

References:

1.”Chemistry of Silicon (Z=14).” Chemistry LibreTexts. Libretexts, 20 June 2017. Web. Available here. A30 June 2017. 
2.”Silica.” Encyclopædia Britannica. Encyclopædia Britannica, inc., n.d. Web. Available here. 30 June 2017. 

Image Courtesy:

1. “SiliconCroda” By Enricoros at English Wikipedia – (Public Domain) via Commons Wikimedia
2. “Zirconia-silica-beads-05mm-03” By Lilly_M – Own work (CC BY-SA 3.0) via Commons Wikimedia