Unit1Topic4 - Structures Flashcards
Properties of a giant ionic lattice
Crystalline High melting points Conducts electricity when liquid Does not conduct electricity when solid Soluble in water
Properties of a simple covalent/covalent molecular structure
Low melting and boiling points (mainly gases)
Does not conduct electricity
Not soluble in water
Soft when solid eg iodine
Properties of a giant covalent structure
Both: high melting and boiling points
insoluble in water
Diamond: does not conduct electricity
extremely hard
Graphite: conducts electricity
slippery soft solidProperties of a giant metallic structure
High melting points (dense and strong) Conducts electricity Conducts heat Malleable (bends) Ductile (can be stretched into wires)
Sodium chloride (giant ionic) conducts electricity when molten but not when solid, explain why.
When molten or dissolved in water the strong electrostatic interactions are overcome and the ions are free to move and carry the current.
Why do ionic compounds have high melting and boiling points?
Large amounts of heat energy required to separate the oppositely charged ions due to the strong ionic bonds.
What is a covalent bond?
A shared pair of electrons between two non-metals.
Why do molecular covalent structures have low melting and boiling points?
Although there are strong covalent bonds between the atoms in the molecules, there are only weak forces of attraction between molecules (van der Waals). Little energy is required to break the bonds.
Examples of simple covalent structures
Carbon dioxide
Water
What is the name of the forces between the molecules in simple covalent structures?
Van der Waals forces
What element are diamonds and graphite made of?
Carbon
How many atoms of carbon surround each carbon atom in diamond?
4
How many atoms of carbon surround each carbon atom in graphite?
3
Why do diamond and graphite both have high melting points?
Strong covalent bonds between the atoms in a giant covalent structure. Lots of heat energy required to separate the atoms.
Which of graphite’s properties means that it can be used as a lubricant?
The layers are only held together by weak intermolecular forces (van der Waals). The layers can slide over each other - making it a slippery soft solid.
