Unit 4. Metallic Bonding Flashcards
Characteristics of metals
good conductors of heat and electricity,
ductile (can be made into wires),
malleable (can be bent into shape) and
shiny when polished.
What is special about v.e in metallic structures
In metals, the valence electrons are free to move throughout the metallic structure. These electrons are described as being delocalised and are frequently referred to as a ‘sea of delocalised electrons’.
Define metallic bonding
the electrostatic attraction between the lattice of positive metal ions and the ‘sea’ of delocalised electrons.
Metallic bonding, like ionic bonding, is described as being non-directional, The metal atoms are ionised, forming positive ions that are arranged in a lattice structure.
Why are metals able to bend in different shapes
If sufficient force is applied to the metal, one layer of metal ions can slide over another without disrupting the metallic bond; the bond remains intact. Bending a metal into shape does not break the metallic bond, instead, the layers of metal ions slide over each other without disrupting the metallic bond.
What is responsible for the high thermal and electrical conductivity of metals
Delocalized electrons in metallic lattice
How do metals conduct electricity
When a potential difference (voltage) is applied across a metal, a direction is imposed on the movement of the delocalised electrons. They are repelled from the negative electrode and move towards the positive electrode. This orderly flow of delocalised electrons in a given direction constitutes the flow of an electric current.
How do metals conduct heat
The delocalised electrons can also conduct heat: the electrons move through the metal, carrying kinetic energy (in the form of vibrations) from the hotter part of the metal to the colder part of the metal. These delocalised electrons are also responsible for the shininess of metals, because they reflect wavelengths of visible light.
What does the strength of the metallic bond rely on
the charge on the metal ion and the ionic radius of the metal ion.
Correlation between metallic bond strength and melting point
the stronger the bond, the higher the melting point.
What determines the density of a metal
Generally, the smaller the ionic radius and the higher the ionic charge, the higher the density of the metal.
What are alloys
Alloys are homogeneous mixtures composed of two or more metals or a metal and a non-metal. In its scientific usage, the term metal refers to a metallic element.
How are alloys produced
by adding one or more metal or non-metal elements to another metal in its molten state, so that the different atoms can mix. As the mixture solidifies, atoms of the different metals or non-metals are scattered through the lattice structure.
Properties of alloys and why
metals are malleable due to the layers in the metallic lattice being able to slide over each other without breaking the metallic bond. The addition of different sized atoms in the alloy means that the layers cannot slide over each other as easily. This results in the alloy being harder than its component metals.
alloy is often stronger, more chemically stable and often more resistant to corrosion
