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Learning Targets/ Content Objectives
Learning Targets/ Content Objectives
Metals are composed of cations that are embedded in a delocalized sea of valence electrons. This means that the electrons do not stay with one atom, rather they are able to move throughout the entire substance. The cations and the electrons are attracted to one another through a Coulombic Attraction which holds the metal atoms together.
In this image you can’t tell which electron came from which cation, this is the idea of delocalization.
How can I tell the number of delocalized electrons?
The number of valence electron determines the amount of electrons in the delocalized sea of electrons. When the charge on the cations and the number of electrons increases the attractions are greater. Additionally, when the ionic radius decreases the attraction increases
What are Alloys?
Alloys are mixtures of metals. There are two types of alloys, interstitial and substitutional. The difference between them is the size of the atoms that are being added to the metal
For an interstitial alloy to form, the component present in the interstitial positions between the solvent atoms must have a much smaller covalent radius than the solvent atoms. Typically, an interstitial element is a nonmetal that participates in bonding to neighboring atoms. The presence of the extra bonds provided by the interstitial component causes the metal lattice to become harder, stronger, and less ductile. For example, steel is an alloy of iron that contains up to 3 percent carbon. Steel is much harder and stronger than pure iron.
An example of interstitial alloy is steel. Steel is made up of iron and carbon. The ratio of carbon to iron affect the properties of steel.
An example of substitutional alloy is Brass that is made up of Copper and Zinc.
Interstitial alloys are more rigid than the primary metal constituent.
Metallic Bonds, Alloys and Metallic Solids
Ionic Solids Vs Metallis Solids
Check for Understanding
Check for Understanding
How can I tell if an alloy is substitutional or interstitial?
Substitutional alloys form between atoms with similar or slightly different atomic radii. However, substitutional alloy form between atoms that have significantly different sizes.
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