University:
University of Cambridge
Course:
0653 IGCSE | Science - Combined
Academic year:

2023
Views:

26

Pages:

3
Author:

anon

IGCSE Coordinated Science:Giant Structure Giant Structure 1 Describe the giant covalent structures of graphite and diamond. Diamond is a form of Carbon Above, each blue blob is a Carbon atom. The structure has billions of atoms forming hexagons and extends in all directions. The Carbon is bonded Covalently (more on that in another topic), and each covalent bond is the same. All these covalent bonds forms a Giant Molecular Structure The covalent bonds are all REALLY strong. So is graphite: Graphite is similar to diamond, as it is also made out of Carbon. However, unlike Diamond where each Carbon atom is joined with 4 other Carbon atoms, in Graphite, each Carbon atom is only joined with 3 other Carbon atoms. Graphite exists in layers, as shown below: Carbon is in group 4 of the Periodic table, so it has four electrons in its outer shell. But in Graphite, only three electrons are used for bonding. Where has the extra electron gone? The spare electron is what we call “delocalized”, so basically, its free to roam around the layers of graphite. The free electron is great as it allows Graphite to conduct electricity and heat as the free electron is there to conduct the electrical charge. 2 Relate their structures to the use of graphite as a lubricant and of diamond in cutting. Graphite Refer back to the diagram above. The layers between the graphite are very weak, so the layers of covalently bonded carbons can easily “slide” over each other, making graphite very soft and slippery, and hence, making it a great lubricant. Diamond The Covalent Bonds joining the Carbons are VERY strong. As a consequence, this makes diamond very hard and strong, hence making it suitable for cutting material. 3 Describe the structure of silicon(IV) oxide (silicon dioxide). Silicon has a giant covalent structure similar to that of diamond. It is also known as a macro molecular structure as there are many many many covalent bonds here. A few properties of silicon dioxide ● High melting point–Very strong silicon-oxygen covalent bonds have to be broken throughout the structure before melting occurs. ● Hard. This is due to fact that there are many strong covalent bonds here. ● Doesn’t conduct electricity. Doesn’t have any delocalized electrons to conduct the charge.