Structures Flashcards
What is an ionic crystal?
An giant lattice formed from ionic bonds
State and explain the properties associated with giant ionic lattices
•High boiling and melting points due to the large number of cations and anions surrounding each other meaning there is more energy required to break these attractions. This also makes them hard.
•brittle
What is meant by the term crystal coordination number?
The number of atoms or ions that are directly bonded to a central atom in a crystal lattice.
Describe the giant covalent lattice of graphite
•Each carbon atom is covalently bonded to 3 other carbon atoms forming layers of hexagonal rings.
•There is 1 delocalised electron per carbon atom.
•There are weak intermolecular forces between the layers.
Describe the giant covalent lattice of diamond
•Each carbon atom is covalently bonded to 4 other carbon atoms in a tetrahedral shape with no delocalised electrons.
Describe and explain the properties of graphite
•Graphite is soft as the intermolecular forces between the layers are weak, allowing them to slide over one another.
•Graphite can conduct electricity as there are delocalised electrons that can carry a current.
Describe and explain the properties of diamond
•very hard as all the carbond are bonded to one another
•very high melting point
•cannot conduct electricity as there are no delocalised electrons.
What are the uses of graphite?
Electrodes- conducts electricity and has a high melting point.
Lubricant/pencil lead- soft/slippery as the layers can slide over each other.
What are the uses of diamond?
Cutting tools- hardest substance on earth
Describe the structure of ice
Due to the presence of hydrogen bonding of water molecules, has a lower density than water but takes up greater volume. These intermolecular forces remain rigid when ice forms and position the molecules further apart than when in liquid state.
What is metallic bonding?
Interactions between the cation metal atoms and there sea of delocalised electrons.
Explain the electrical conductivity of ionic compounds?
When solid ionic compounds cannot conduct electricity as there are no delocalised electrons to carry the current. Ionic compounds must be molted or dissolved.
Explain the electrical conductivity of covalent compounds?
Covalent compounds cannot conduct electricity as there are no free charged particles.
Explain the electrical conductivity of metals?
Metals conduct electricity due to the electron delocalisation. Electrical conductivity increases with the number of delocalised electrons per atom.
Explain the hardness of metals?
The hardness of metals depends on the number of electrons delocalised per atom, the more
delocalised electrons you have, the harder the metal.
Explain how the hardness of metals could be improved
Metals are very malleable and so could be turned into alloys to increase the hardness. This involves combining different metals with different sized atoms to disort the neat layers making it harder for the layers to slide over one another.
