Potassium chloride is an ionic compound. The ions in potassium chloride are held together by strong electrostatic force of attraction. A lot of energy is needed to break down these bonds, hence the high melting point.
Month: July 2020
Explain, using structure and bonding, why diamond is very hard.
Diamond has a giant molecular structure. It consists of a large number of carbon atoms covalently bonded to one another to form a giant tetrahedral structure. This structure is a strong and rigid structure, making diamond very hard.
Explain, using structure and bonding, why graphite can conduct electricity.
Graphite has a giant molecular structure. It is made up of layers of carbon atoms covalently bonded. Each layer is made up of carbon atoms covalently bonded to one another in hexagonal rings. Each carbon atom is covalently bonded to 3 other carbon atoms, hence each carbon atom has 1 valence electron not involved in bonding. These electrons are delocalised, and can move freely within the layer to conduct electricity.
Explain, using structure and bonding, why carbon dioxide has low melting point and boiling point.
Carbon dioxide is a simple covalent compound, consisting of discrete molecules. The molecules are held together by weak intermolecular forces of attraction. Very little energy is needed to break these weak bonds, hence carbon dioxide has low melting point and boiling point.
Total Internal Reflection and the Brilliance of Diamonds
A diamond is cut in such a way that the flat shape of the crown allows for the maximum number of light rays to either reflect off the crown or refract into the diamond.
The critical angle of diamonds will be small as the refractive index of diamond is high.
The shape and angle of the pavillion is such that most light rays falling on it will have an angle of incidence greater than the critical angle. This allows for total internal reflection to occur, causing light rays to reflect multiple times within the diamond, and leave the diamond through the crown.
The multiple light rays leaving the crown of the diamond makes it look more brilliant to an observer looking at the crown of the diamond.
