Structures Flashcards
4 types of structures
Giant Ionic Lattice
Covalent Molecular
Giant Covalent Structure
Giant Metallic Structure
Giant ionic lattice example
Sodium chloride
Magnesium Oxide
Giant Ionic Lattice Properties
1) High Melting / Boiling Point
2) Hard but brittle
3) Soluble in Water
4) Conducts electricity when molten of in a solution
Why does a giant ionic lattice have a high melting point
To melt, a large number of strong ionic bonds must be broken. This requires a large amount of energy
why is a giant ionic lattice hard but brittle
A slight shift in ions can move the layer of ions. Ions of the same charge repel each other
Why is a giant ionic lattice soluble in water
Water molecules surround ions and hydrate them
Why does a giant ionic lattice conduct electricity when molten or in a solution but not as a solid
Ions can only move when molten or in a solution to conduct. As a solid they are held in a strong lattice
Covalent molecular examples
Iodine, carbon dioxide, water
Properties of covalent molecular
1) low melting and boiling points
2) most not soluble in water but some are
3) don’t conduct electricity
4) soft when solid
Why does covalent molecular have low melting and boiling points
Only the Van der Waal forces between molecules need to be broken and these are weak so only a small amount of energy is needed
Why doesn’t covalent molecular conduct electricity
No charged particles like ions or free electrons present so there is no attraction to electrodes
Why is covalent molecular soft when solid
Weak Van der Waal forces are easy to shift around
Allotropes of carbon
Diamond, graphite and Graphene
Properties of diamond
1) Very high melting point
2) insoluble in water
3) doesn’t conduct electricity
4) very hard substance
Why does diamond have a very high melting point (3500°C)
Many strong covalent bonds must be broken
Why doesn’t diamond conduct electricity
There is no free electrons or ions
Why is diamond a very hard substance
It has a highly regular structure
Properties of graphite
1) High melting point
2) insoluble in water
3) conducts electricity
4) soft and slippery
Why does graphite have a high melting point
Many strong covalent bonds must be broken which requires a lot of energy
Why does graphite conduct electricity
Has a layer of free electrons that can flow as a current
Why is graphite soft and slippery
The layers slide over each other easily. It’s used in pencils and lubricants
Properties of Graphene
1) Very light and thin
2) transparent
3) 100 times stronger than steel
4)very good conductor
5) used in batteries and solar cells
Properties of a giant metallic structure
1) High melting points
2) malleable and ductile
3) conducts heat and electricity
4) insoluble in water (many react)
Why do giant metallic structures have high melting points
The bond between the free electrons and the positive metal ions is very strong and requires a lot of energy to break
Why are giant metallic structures malleable and ductile
The metal ions are arranged in layers and slip over each other easily
Why do giant metallic structures conduct heat and electricity
Delocalised electrons are free to move so they can carry an electrical current
Allotrope
Different forms of the same element in the same physical state
Ductile
Can be drawn out into wires
Malleable
Can be hammered into shape
What is metallic bonding
The attraction between delocalised electrons and positive ions in a regular lattice
What is an alloy
A mixture of two or more elements, at least one of which is a metal, and the resulting mixture has metallic properties
Examples of alloys
Brass = copper + zinc (5-45%)
bronze = 60% copper + 40% tin
gold = gold + silver
steel = iron + carbon
Properties of alloys
Harder than pure metals
still conducts electricity
Why is an alloy is harder than pure metal
The different sizes disrupts regular layers making it harder for layers to slide over each other
Why can an alloy still conduct electricity
Free electrons can still move in the structure
