1.4.9 Properties of Metallic Substances Flashcards
Metals form
giant metallic lattices
Metals form giant metallic lattices in which the metal ions are surrounded by
a ‘sea’ of delocalised electrons
The metal ions are often packed in
hexagonal layers or in a cubic arrangement
Layers of copper ions (the delocalised electrons are not shown in the diagram)
If other atoms are added to the metal structure, such as carbon atoms, this creates
an alloy
Alloys are much stronger than pure metals, because
the other atoms stop the layers of metal ions sliding over each other easily
The strength of the metallic attraction can be increased by:
- Increasing the number of
delocalised electrons per metal atom
The strength of the metallic attraction can be increased by:
- Increasing the
positive charges on the metal centres in the lattice
The strength of the metallic attraction can be increased by:
- Decreasing
the size of the metal ions
Metallic compounds are
malleable
When a force is applied
the metal layers can slide
The attractive forces between the metal ions and electrons
act in all directions
So when the layers slide, the metallic bonds are
re-formed
The lattice is not broken and has
changed shape
Atoms are arranged in layers so the layers can slide when force is applied diagram
Metallic compounds, as well as malleable, are
strong and hard
Metallic compounds are strong and hard, due to
the strong attractive forces between the metal ions and delocalised electrons
Metals can
conduct electricity when in the solid or liquid state
In the solid and liquid states, there are
mobile electrons which can freely move around and conduct electricity
When a potential difference is applied to a metallic lattice, the delocalised electrons
repel away from the negative terminal and move towards the positive terminal
As the number of outer electrons increases across a period, the number of
delocalised charges also increases
As the number of outer electrons increases across a period, the number of delocalised charges also increases:
Sodium = 1 outer electron
Magnesium = 2 outer electrons
Aluminium = 3 outer electrons
Therefore, the ability to conduct electricity also
increases across a period
How metals conduct electricity diagram
Since the bonding in metals is
non-directional
Since the bonding in metals is non-directional, it does not really matter how
the cations are oriented relative to each other
Metals are good
thermal conductors due to the behaviour of their cations and their delocalised electrons
When metals are heated, the cations in the metal lattice
vibrate more vigorously as their thermal energy increases
These vibrating cations transfer their
kinetic energy as they collide with neighbouring cations, effectively conducting heat
The delocalised electrons are not bound to
any specific atom within the metal lattice and are free to move throughout the material
When the cations vibrate
they transfer kinetic energy to the electrons
The delocalised electrons then carry
this increased kinetic energy
The delocalised electrons then carry this increased kinetic energy and
transfer it rapidly throughout the metal, contributing to its high thermal conductivity.
Metals have high
melting and boiling points
Metals have high melting and boiling points, this is due to
the strong electrostatic forces of attraction between the cations and delocalised electrons in the metallic lattice
Metals have high melting and boiling points, these require
large amounts of energy to overcome
Metals have high melting and boiling points, as the number of
mobile charges increases across a period, the melting and boiling points increase due to stronger electrostatic forces
