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
Cannot conduct electricity unless molten or dissolved in water sp that the ions are mobile and a can hold a current.
Some are soluble in water due to the attraction between the polar water molcules and the charged ions.
What ionic lattices are soluble in water?
Most chlorides and group 1 salts
All metal nitrates
The greater the ionic charge, the less able the compound is to dissolve in water.
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
Why are diamond and graphite insoluble in water?
Polar molecules are not attracted to neutral carbon atoms.
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.
Explain the strength of melting and boiling points in metallic lattices
High melting and boiling points due to the strength of the bonds as weell as the number of delocalised electrons.
The greater the number of delocalised electrons per cation, the greater the melting and boiling point.
What are features of simple molecular forces?
Low melting and boiling points and so are usually liquid or gas at room temperature.
Poor conductors as they have no charged atoms
Insoluble in water
What are simple molecular lattices?
Lattices made up of molecules covalently bonded but held together by weak van der waal forces.
Iodine as a simple molecular lattice
Soft and volatile as the units of iodine are held together by van der Waals forces. If heated solid iodine gives off a purple gas.
