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.
What are transition metals?
Elements whose atoms have an incomplete d-sublevel, or can give rise to cations with an incomplete d-sublevel.
Which electrons are delocalised during metallic bonding?
3d and 4s sublevel electrons are delocalised.
- This is because the d electrons are close in energy to the outer s electrons.
Why is metallic bonding strong?
Due to the large number of delocalised electrons and the large positive charge on the metal cations.
What is the trend of melting points for transition metals?
There is a little trend due to their similar atomic radii and large delocalised electron number.
- Opposite trend to number of oxidation states that transition metals can form.
- Mn has the lowest melting point and there is an increasing function on the left and decreasing function on the right.
Why are transition metals good at conducting electricity?
- Large number of delocalised electrons which are free to move.
- These delocalised electrons move around the structure and carry charge through the structure.
Why is copper good for conducting electricity?
- Uncreactive
- Lots of delocalised electrons - more efficient conductor.
