Metals

 Properties of elements determine what we can use them for.  For example, tungsten has the highest melting point of any metal ( C) but it is very ductile. For these reasons we use it in light bulbs as the filament.

 Metal atoms lose electrons to become stable.  If there is a nonmetal around to bond with, they will give it their electrons and become part of a stable compound.

 If there is not a nonmetal around, they have another solution.  They become cations with free electrons floating around them.  A metallic bond is the attraction between the cation and the free electrons around it.

 The cations in a metal form a lattice (like the lines on graph paper) that is held in place by strong metallic bonds between the cations and the surrounding valence electrons.  Because the total number of electrons does not change, the total metal is neutral.

 Metallic bonds in some metals are stronger than in other metals.  The more valence electrons in the shared pool, the stronger the metal will be.  Alkali metals can only contribute 1 electron each to the pool so they are weak.  Transition metals contribute more electrons so they are stronger.

 The stronger the metal, the higher its boiling point.

 Metals’ properties are caused by the movement of electrons within the metal lattice.

 Metals conduct electric current.  Electric current is a flow of charged particles.  The pool of shared electrons in metals act like a reservoir for electric current to pass through.

 Malleability is flexibility.  The metal lattice is flexible compared to a rigid ionic compound lattice (remember those shatter when struck).  When a metal lattice (a piece of metal) is struck, the ions shift slightly but do not break their metallic bonds.  For this same reason, metals are ductile.

 Alloys are mixtures of 2 or more elements (at least 1 of the elements must be a metal).  Alloys have the properties of metals.

 Copper alloys  Steel alloys  Others

 Copper alone is a soft metal.  Bronze = copper and tin  Bronze is hard and durable.  Brass = copper and zinc  Brass is softer and shinier than bronze but not as durable.

 Steel = iron + carbon  Carbon atoms fill in spaces in the iron lattice and add strength.  Stainless steel = iron + chromium  The chromium keeps the steel from rusting, but stainless steel is more brittle than steel containing carbon.  Other steels contain sulfur, manganese, phosphorus, and/or silicon.

 Alloys can be made to suit different needs based on what elements are added to them.

 Pure gold (24 karat) is easily worn and bent.  Adding silver, copper, nickel, or zinc to gold (and reducing its karat or purity) makes it stronger and more durable.

 Aluminum is light but weak.  When copper or manganese are added to aluminum it gains strength without gaining excessive weight.  This is used to build airplane bodies.

 Magnesium burns when exposed to air.  An aluminum-magnesium alloy stabilizes magnesium.  This compound is used to make very lightweight airplane parts.

 Bridge cables need to resist stretching and pulling while supporting a great amount of weight.  Special steel alloys are used for this.