S2.3 - metallic model Flashcards
What is a metallic bond?
Metallic bond - electrostatic attraction between a lattice of cations and a sea of delocalised electrons.
What does the strength of a metallic bond depend on?
- Charge on cation
- Radius of cation
- Number of delocalised electrons
What is metallic character?
Loss of control over their outer shell electrons in metals.
What are 6 properties of metals?
- Good electrical conductivity
- Good thermal conductivity
- Malleable (can be shaped under pressure)
- Ductile (can be drawn out into threads)
- High melting points
- Shiny, lustrous appearance
Why is metal a good electrical conductor and what are examples of uses?
Delocalised electrons are highly mobile and can move through the metal structure in response to an applied voltage.
- Electrical circuits use copper.
Why is metal a good thermal conductor and what are examples of uses?
Delocalised electrons and closely packed ions enable efficient transfer of thermal energy.
- Pots and pans used for cooking.
Why is metal malleable and what are examples of uses?
Movement of delocalised electrons is non-directional and random throughout the cation lattice, so the metallic bond remains intact while the conformation changes under applied pressure.
- Machinery, structural components and vehicles.
Why is metal ductile and what are examples of uses?
Movement of delocalised electrons is non-directional and random throughout the cation lattice, so the metallic bond remains intact while the conformation changes under applied pressure.
- Electrical wires and cables.
Why do metals have high melting points are what are examples of uses?
A lot of energy is required to overcome the strong electrostatic forces of attraction in the metallic bond to separate the atoms.
- High speed tools and turbine engines.
Why are metals shiny and lustrous and what are examples of uses?
Delocalised electrons in the metal crystal structure reflect light.
- Ornamental structures and jewellery.
What are trends in melting points of metals across the period?
Across the period, melting points of metals increases as there is increased ENC, meaning a higher charge density and smaller ionic radii, resulting in a stronger attraction between electron and nucleus.
- Lower degree of reactivity
What are trends in melting points down the group?
Down the group, melting points of metals decreases as there is a larger ionic radii and a weaker attraction between electron and nucleus, which requires less energy to overcome, as well as lower ENC due to the addition of shells.
- Higher degree of reactivity
What is an alloy?
Homogeneous mixture of at least 1 metal and another substance in a metallic bond.
Why are alloys hard?
Alloys are hard as the layers are disrupted, meaning that the atoms cannot slide easily or change shape when a pressure or force is applied.
