Structure of Metals and Alloys

Structure of Metals

Metals are made up of closely packed positive ions (cations) surrounded by a sea of delocalised electrons, which are the electrons in the outermost shell that are not associated with a single atom but are free to move throughout the entire structure.
The arrangement of the atoms in a metal crystal is in a regular pattern or lattice, which is often cubic.
The strong electrostatic forces between the positive metal ions and negative electrons are called metallic bonds. These bonds hold the structure together and give metals their unique properties.
The delocalised electrons in the metal allow for electricity and heat to be conducted throughout the structure, making metals excellent conductors.
The ability of metals to be hammered or rolled into thin sheets is known as malleability, and their ability to be drawn into a wire is known as ductility. Both these properties are due to the layers of positive ions in a metal being able to slide over each other when a force is applied, without disrupting the metallic bonding.

Alloys are homogeneous mixtures of two or more elements, where at least one element is a metal. Most alloys are solid solutions, which means they have a similar structure to metals but the different element atoms replace or fit into the gaps between the metal atoms in the lattice.
The different-sized atoms in an alloy cause a disruption to the uniform lattice structure seen in pure metals. This distortion of the layers prevents them from sliding over each other easily when a force is applied.
Therefore, alloys are usually harder and stronger than the pure metal alone, because the atoms of different sizes prevent the layers from sliding over each other.
Common examples of alloys include brass (copper and zinc) and steel (iron and carbon). Different alloys have different properties making them useful for different applications. For example, steel is used in building construction for its strength, while brass is used for electrical fittings due to its corrosion resistance.
One noteworthy characteristic of alloys is that they often have greater corrosion resistance than their pure metal counterparts.