Week 3 Flashcards
What are the three types of bonds?
Metallic bonds - Form between metal atoms Ionic bonds - Form between metal and non-metal atoms Covalent bonds - Form between non-metal atoms
Properties of ionic solids?
High melting and boiling points
Brittle
Good electrical conductivity when molten or in aqueous state
Explain the high melting and boiling points of ionic solids?
Large amounts of energy is needed to overcome the strong electrostatic forces between the oppositely charged ions.
What happens to ions in the solid state?
They are in fixed positions
What happens to ions in the molten state?
They are mobile and thus can conduct a current
What happens to ions that are soluble in water?
They create a conducting solution since the ions are free to move
What do metals characterised by low ionisation energy indicate?
Their valence electrons are not strongly held
What happens to metals with low ionisation energy?
They become delocalised
What do delocalised electrons result in?
The atoms become:
Positive ions
Attracted to the delocalised electrons
Achieving a stable electron configuration
Properties of metallic bonds?
High electrical conductivity High thermal conductivity Malleable and ductile Wide range of boiling points and melting points Relatively high density
Explain the high electrical conductivity of metallic bonds?
Valence electrons are highly mobile and hence can conduct charge
Explain the high thermal conductivity of metallic bonds?
When a substance is heated, the particles vibrate more rapidly
Delocalised electrons transfer this energy readily as they move through the lattice
Explain the malleability and ductility of metallic bonds?
Can be hammered into sheets and drawn into wires
Metallic bonds are non directional
Layers of positive ions can simply slip over each other
Explain the wide range of boiling and melting points of metallic bonds?
The greater the number of valence electrons, the stronger the bond
Explain the relatively high density of metallic bonds?
Strong electrostatic and close packing of the ions means that metals are generally dense
This increases with the number of valence electrons per atom
