Chapter 5 Flashcards
What are the properties of most metals?
High melting points, conduct electricity and heat well in the solid state, have lustre, have high density, are malleable, ductile and are often hard.
How do most metals bond and what is this bonding called?
Positively charged metal ions form a 3-D lattice. This is called the metallic bonding model.
How do the ions form into a lattice?
They form when each metal atom releases one or more electrons of its outer valence electrons, which become the property of the lattice.
Why are electrons in the lattice known as delocalised?
Because the electrons can move freely throughout the lattice.
How is the lattice held together?
Strong electrostatic attraction between the positively charged metal ions and the negatively charged delocalised electrons.
How does the metallic bonding model explain the high melting points of metals?
Strong electrostatic forces between positive ions and negative free electrons hold the lattice more strongly together, so require more energy to melt.
How does the metallic bonding model explain metals being good conductors of electricity?
Free electrons allow the positive to negative ‘flow’ of electrodes, allowing effective passage of electricity through lattice.
How does the metallic bonding model explain metals being malleable and ductile?
When a force causes metal ions to move, the free electrons cause the layers of ions to move together.
How does the metallic bonding model explain metals being good conductors of heat?
Because the delocalised electrons are free to move, there is more space for them to bounce around and bump into each other, transferring heat across the lattice.
Describe alloys
They have properties different from those of pure metals. they are generally harder than pure metals but poorer conductors of electricity.
Name 2 types of alloy
Substitutional alloys and interstitial alloys.
How do you change the malleability and strength of an alloy?
Alter the crystal size by work hardening and heat treatment.
