Chapter 6 metals

Chapter 6
Metals
Why is all of this stuff important?
Properties of elements determine what we can use them for.For example, tungsten has the highest melting point of any metal (34100C) but it is very ductile. For these reasons we use it in light bulbs as the filament.
Metal Atoms
Metal atomsloseelectrons 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.
Metallic Bonds
If there is not a nonmetal around, they have another solution.They become cations with free electrons floating around them.Ametallicbond is the attraction between thecationand the freeelectronsaround it.
Metallic Bonds
Thecationsin a metal form a lattice (like the lines on graph paper) that is held in place by strong metallic bonds between thecationsand the surroundingvalence electrons.Because the total number ofelectronsdoes not change, the total metal isneutral.
Metallic Bonds
Metallic bonds in some metals are stronger than in other metals.Themorevalence electrons in the shared pool, the stronger the metal will be.Alkali metalscan only contribute 1 electron each to the pool so they are weak.Transition metalscontribute more electrons so they are stronger.
Remember
The stronger the metal, thehigherits boiling point.
Metal Properties
Metals’ properties are caused by the movement of electrons within the metal lattice.
Conductivity
Metals conduct electric current.Electric current is a flow of charged particles.The pool of shared electrons in metals act like areservoirfor electric current to pass through.
Malleability
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 ionsshift slightlybut do not break their metallic bonds.For this same reason, metals areductile.
Alloys
Alloysare mixtures of 2 or more elements (at least 1 of the elements must be a metal).Alloys have the properties of metals.
Types of Alloys
Copper alloysSteel alloysOthers
Copper Alloys
Copper alone is a soft metal.Bronze= copper and tinBronze is hard and durable.Brass= copper and zincBrass is softer and shinier than bronze but not as durable.
Steel Alloys
Steel= iron + carbonCarbon atoms fill in spaces in the iron lattice and add strength.Stainless steel= iron + chromiumThe 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.
Other Alloys
Alloys can be made to suit different needs based on what elements are added to them.
Why Alloys?
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.
Why Alloys?
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.
Why Alloys?
Magnesium burns when exposed to air.An aluminum-magnesium alloy stabilizes magnesium.This compound is used to make very lightweight airplane parts.
Why Alloys?
Bridge cables need to resist stretching and pulling while supporting a great amount of weight.Special steel alloys are used for this.