HOME PAGE * SEARCH * KS3 Basic Science Quizzes for students students aged ~13-14

GCSE level Biology * Chemistry * Physics age ~14-16 * Advanced pre-university Chemistry ~16-18

4d. Silicon and silicon dioxide giant covalent structures

Also, a comparison of the structure and physical properties of carbon dioxide and silicon dioxide

[Author © Dr Phil Brown PhD: Doc Brown's chemistry exam revision notes on larger covalent structures suitable for students of UK GCSE Science level AQA, Edexcel, OCR, WJEC and CCEA GCSE chemistry courses, ~US grades 9,10, 11, 12 chemistry, also useful for more advanced pre-university A level chemistry courses [page updated April 16th 2026 *]

[email doc b with any query ]  *  [privacy policy, cookies, disclaimer]  *  ]SEARCH science website]

All my GCSE level chemistry revision notes

All my advanced level chemistry revision notes

All my structure and bonding notes

Part 4 Giant covalent structures and other big molecules

GCSE level practice exam question QUIZ

Foundation tier (easier) m/c QUIZ on structure, properties & chemical bonding of materials

Higher tier (harder) m/c QUIZ on structure, properties and chemical bonding of materials
  • Pure elemental SILICON (not the oxide) has the same molecular structure as diamond and similar properties, though the 3D giant covalent bond network is not as strong, so elemental silicon is not as high melting as carbon in the form of diamond.
    • The molecular diagram is the same for Sin, where n is a huge number!
      • (Its the same ball and stick diagram I used for diamond, but the atoms would be a bit bigger)
    • Silicon melts at 1400oC, and has poor electrical conductivity (no free electrons or ions) and won't dissolve in any solvent.
    • The silicon in the transistors of electronic devices is 'doped' with other elements to increase its electrical conductivity.
  • SILICON DIOXIDE (SILICA) (SiO2)n where n is an extremely large number of silicon and oxygen atoms!
    • Many naturally occurring minerals are based on –O–X–O– linked 3D structures where X is often silicon (Si) and aluminium (Al), three of the most abundant elements in the earth's crust.
    • Silicon dioxide ('silica') is found as quartz in granite (igneous rock) and is the main component in sandstone – which is a sedimentary rock formed the compressed erosion products of igneous rocks.
      • (c) doc bLooking at the diagram on the right of silica, each silicon atom (black blobs) forms four strong covalent bonds with the linking oxygen atoms (yellow blobs).
      • You can also see from the diagram that there are two oxygen atoms to every silicon atoms giving the empirical formula SiO2.
      • Again like diamond, theoretically all the atoms in a silica crystal are linked together by a strong 3D covalent bond network giving a strong rigid structure.
      • It takes a lot of energy to break (overcome) the strong silicon-oxygen bonds in the giant covalent lattice of silicon dioxide (silica), hence the high melting point of 1600oC.
    • Therefore Silica (SiO2) is a very hard substance with a very high melting point and won't dissolve in any solvent.
    • There are no free electrons so silicon dioxide doesn't conduct electricity.
    • Many more minerals that are hard wearing, rare and attractive when polished, hold great value as gemstones, but sand is also mainly silica, but not quite as valuable!

A comparison of carbon dioxide and silicon dioxide

Carbon and silicon are in the same group IV and have the same oxide formula in terms of their valency of 4

BUT they have very different physical properties.

 Its all about the nature of the bonding situation!

Property Carbon dioxide, CO2 Silicon dioxide, SiO2
Structure Small individual covalently molecules

O=C=O...O=C=O...O=C=O

Strong covalent double bonds between the carbon and oxygen atoms within the molecule itself, BUT weak intermolecular forces between the molecules (...)

 (c) doc b3D giant covalent network of strong Si-O-Si bonds.

Weak intermolecular bonding versus strong giant covalent bonding.
Physical state at room

 

 GAS

Sublimes at -78oC, because of the weak intermolecular forces

 SOLID

Melts at 1710oC, , because of the very strong inter-atomic forces - much higher thermal kinetic energy needed to break down the structure
Physical strength Weak brittle solid below -78oC, because of the weak intermolecular forces Very strong hard material.
Solubility Will dissolve in many solvents e.g. water or organic liquids. The solvent can overcome the weak intermolecular forces to dissolve the molecules. Will NOT dissolve in any solvents like water or organic liquids. The solvent cannot overcome the strong covalent bonds to dissolve the giant molecules.
Conductivity The solid crystal is a poor conductor of thermal energy and electricity The solid crystal is a poor conductor of thermal energy and electricity

You can also compare the similarity of carbon (diamond), silicon Si and silicon dioxide SiO2 - the bonding diagrams say it all.

All three have a similar 3D giant covalent structure, like the one above or on the right, which could be carbon (diamond) or the element silicon.

They will therefore share a similar set of physical properties described above for silicon dioxide.

What next?

GCSE level practice exam question QUIZ

Foundation tier (easier) m/c QUIZ on structure, properties & chemical bonding of materials

Higher tier (harder) m/c QUIZ on structure, properties and chemical bonding of materials

Recommend next:

Covalent bonding in polymers and 1, 2 and 3 'dimension' concepts in macromolecules

Sub-index for: Part 4 Giant covalent structures and other big molecules

Index for ALL chemical bonding and structure notes

Use Google search box
Website content © Dr Phil Brown 2000+. All copyrights reserved on revision notes, images, quizzes, worksheets etc. Copying of website material is NOT permitted. Exam revision summaries & references to science course specifications are unofficial. Chemistry bonding notes for GCSE and A level chemistry courses, Revision notes on structure, properties & uses of silicon based on the syllabus-specifications for students taking IGCSE/GCSE level chemistry examinations, summary revision notes and key points on structure, properties & uses of silicon for students taking the AQA igcse/gcse chemistry notes on structure, properties & uses of silicon, Edexcel gcse chemistry notes on structure, properties & uses of silicon,  OCR 21st century GCSE chemistry notes on structure, properties & uses of silicon, OCR gateway GCSE chemistry notes on structure, properties & uses of silicon, WJEC gcse chemistry notes on structure, properties & uses of silicon, CCEA gcse chemistry notes on structure, properties & uses of silicon for students taking CIE Cambridge igcse chemistry, exam revision notes on structure, properties & uses of silicon, useful for US grade 9-10 chemistry courses, importance of structure, properties & uses of silicon dioxide (silica) in GCSE level chemistry, What you need to know about structure, properties & uses of silicon dioxide (silica) for GCSE level chemistry, Explaining the use of structure, properties & uses of silicon dioxide (silica) knowledge in GCSE level chemistry, Examples of structure, properties & uses of silicon dioxide (silica) explained when studying GCSE level chemistry, What is significant about structure, properties & uses of silicon dioxide (silica), describing the theory of structure, properties & uses of silicon dioxide (silica) when studying GCSE level chemistry, revision notes for structure, properties & uses of silicon dioxide (silica) in exams, online exam help for structure, properties & uses of silicon dioxide (silica), revision notes about structure, properties & uses of silicon dioxide (silica), what do I need to learn about structure, properties & uses of silicon dioxide (silica) for by GCSE chemistry exam? help to understand the structure, properties & uses of silicon dioxide (silica) topic in preparation for GCSE chemistry exam question, how to prepare for questions involving structure, properties & uses of silicon dioxide (silica) in a GCSE chemistry examination? Explaining importance of comparing gaseous structure of CO2 with giant covalent structure of SiO2 in GCSE level & A level chemistry, What you need to know about comparing gaseous structure of CO2 with giant covalent structure of SiO2 for GCSE level & A level chemistry, Explaining use of comparing gaseous structure of CO2 with giant covalent structure of SiO2 knowledge in GCSE level & A level chemistry, Examples of comparing gaseous structure of CO2 with giant covalent structure of SiO2 explained when studying GCSE level & A level chemistry, What is the significance of comparing gaseous structure of CO2 with giant covalent structure of SiO2 in GCSE level & A level chemistry, describing explaining theory of comparing gaseous structure of CO2 with giant covalent structure of SiO2 when studying GCSE level & A level chemistry, exam revision notes for comparing gaseous structure of CO2 with giant covalent structure of SiO2, online help for understanding comparing gaseous structure of CO2 with giant covalent structure of SiO2 in GCSE chemistry, what do I need to learn about comparing gaseous structure of CO2 with giant covalent structure of SiO2? what do I need to know about comparing gaseous structure of CO2 with giant covalent structure of SiO2 for GCSE chemistry exams, how to prepare for questions on comparing gaseous structure of CO2 with giant covalent structure of SiO2 in GCSE chemistry examination? comparing gaseous structure of CO2 with giant covalent structure of SiO2 for syllabus-specifications for students taking the IGCSE/GCSE level & A level chemistry examinations, summary revision notes key points on comparing gaseous structure of CO2 with giant covalent structure of SiO2 for students studying AQA igcse/gcse/A level chemistry notes on comparing gaseous structure of CO2 with giant covalent structure of SiO2, Edexcel gcse/A level chemistry notes on comparing gaseous structure of CO2 with giant covalent structure of SiO2,  OCR 21st century GCSE/A level chemistry notes on comparing gaseous structure of CO2 with giant covalent structure of SiO2, OCR gateway GCSE/A level chemistry notes on comparing gaseous structure of CO2 with giant covalent structure of SiO2, WJEC gcse/A level chemistry notes on comparing gaseous structure of CO2 with giant covalent structure of SiO2, CCEA gcse/A level chemistry notes on comparing gaseous structure of CO2 with giant covalent structure of SiO2, CIE Cambridge igcse/A level chemistry, IB advanced level chemistry notes on comparing gaseous structure of CO2 with giant covalent structure of SiO2 useful for US grade 9, 10, 11 & 12 chemistry & AP honors chemistry courses

TOP OF PAGE