chapter 8 (p 228-231) chemistry mr. gilbertson

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)