chapter 8 (p 228-231) chemistry mr. gilbertson
TRANSCRIPT
Chapter 8 (p 228-231)
Chemistry
Mr. Gilbertson
Metals consist of closely packed cations floating in a “sea of electrons”.
Valence electrons are said to be “delocalized” because they are not specifically associated with any one metal atom.
All of the atoms are able to share the electrons.
The electrons are not bound to individual atoms.
Melting points – vary greatlyMercury – liquid at room tempTungsten – MP 3422 o CGenerally MP and BP are moderately
highMP not as extreme as BP, cations are
mobile so not as much energy is required to move past one another
BP is higher because cations must be separated which takes much more energy
Metal cations can be pushed or pulled past each otherDuctile – can be drawn into wireMalleable – can be hammered into sheets
Electrons act as a lubricant, allowing cations to move past each other
Durable – strong attraction to electrons
Conductivity of metalsDelocalized electrons are free to moveMovement of mobile electrons around
cations allows an electric current to flowWhen electrical potential is applied to a
metal electrons are forced to metals have less “resistance”
Delocalized electrons move heat from one place to another much more quickly than in materials without mobile electrons
Luster – shiny when smooth and cleanCaused by interaction of mobile
electrons and photons of lightHardness and strength
Increases with an increase in the number of delocalized electrons.
Transition metals are generally harder (Cr, Fe, Ni)
Alkali metals are soft (only 1 delocalized electron)
Mixtures of two or more elements, at least one of which is a metal.
Made by melting, mixing, then cooling the metals.
May contain non-metals like carbon.
Properties are superior to their components.
Sterling silver92.5% Ag, 7.5% CuHarder than silver
Bronze7:1 Cu to Sn (tin)
Stainless SteelFe 80.6%, Cr 18%, C 0.4%, Ni 1%
Cast Iron-Fe 96%, C 4%
Two types of formation:Substitutional alloys
Similar size atoms – replacement
Interstitial alloys Different size atoms – smaller ions fill interstices (spaces between atoms)