Metals notes

Properties of metals

good conductors of electricity (current is a flow of electrons) (MS/ m) (mega siemens per metre)
heat (position of atoms leads to passing the KE from one atom to another)
  1. malleable - shaped or beaten. - because the cations can be moved around and realign within the sea of delocalised electrons
  2. ductile - drawn into a wire - because the cations can be moved around into a wire and realign within the delocalised sea of electrons
  3. Melting points range - dependent on conduction of heat. (change of state from solid to a liquid)
  4. Boiling point relatively high (change of state from liquid to a gas)
  5. generally high density - (mass / vol) (g/mL)
  6. lustrous when cut
  7. hard , high tensile strength

Metallic bond
metalbond.GIF

Metallic bonds are strong electrostatic interactions that form between metal atoms. The structure of metallic bonds is much different from that of covalent and ionic bonds. While ionic bonds join metals to non-metals, metallic bonds join a bulk of metal atoms.
In metallic bonds, the valence electrons from the s and p orbitals of the interacting metal atoms delocalize. That is to say, instead of orbiting their respective metal atoms, they form a "sea" of electrons that surrounds the positively charged atomic nuclei of the interacting metal ions (Figure 0). The electrons then move freely throughout the electron sea. The characteristics of metallic bonds explain a number of the unique properties of metals:
  • Metals are good conductors of electricity because the electrons in the electron sea are free to flow and carry electric current.
  • Metals are ductile and malleable because local bonds can be easily broken and reformed.
  • Metals are shiny because light cannot penetrate their surface; the photons simply reflect off the electrons. However, there is an upper limit to the frequency at which the photons are reflected, although this frequency is generally too high to be visually perceived.
Metallic bonds can occur between different elements, forming an alloy. Aluminum foil and copper wire are examples of metallic bonding in action (Figure 1).
Metallic bonds are mediated by strong attractive forces. This property contributes to the low volatility, high melting and boiling points, and high density of most metals. The group-XII metals zinc, cadmium, and mercury are exceptions to this rule.
Structure of Metal


Working metals
hardening by quenching, annealing etc
How does this work
hardening - hammering and working a metal cause the crystal grains to rearrange into a harder strucutre. - the downs side is that they can become stiff and brittle. - the crystal grains develop slight faults in the lattice structure making cations align opposite each other. - hence repulsion

Quenching
This process heats the metal to a moderate temp and the atoms in the lattice are cooled quickly by plunging the metal into water the result is small metal crystal. that make sthe metal harder - good for baldes - but brittle - your sword might snap.

Annealing
This process involves heating the metal to a moderate temp and the atoms in the lattice are allowed to cool slowly making large crystals. - because metals crystals can grow in any direction to no preordained pattern the process leads to large crystals that are more ductile.

Tempering
This is a process combining both of the above processes - first quench - then re heat to a low temp and grow the crystals a bit more and this increases the hardness and makes it more durable.

Alloys -
main idea a mixture of 2 or more metals which alters the properties of each. Eg brass a mixture of copper and tin - copper stable and flexible, tin, more reactive and harder than copper the result is the brass we use for taps.

Metals and Alloys.pptx

Some extra metals information - from Boundless -
https://www.boundless.com/chemistry/liquids-and-solids/types-crystals/metallic-crystals/

Metallic Crystals

Metallic crystals are held together by metallic bonds, electrostatic interactions between cations and delocalized electrons.

  1. external image goldnuggetusgov.jpeg
fig. 1=====Gold=====
Gold is a noble metal; it is resistant to corrosion and oxidation.
  • Atoms in metals lose electrons to form cations. De-localized electrons surround ions in the electron cloud. Metallic bonds (electrostatic interactions between the ions and the electron cloud) hold the metallic solid together. Atoms are arranged like closely packed spheres.
  • Because outer electrons of metal atoms are delocalized and highly mobile, metals have electrical and thermal conductivity. The free electron model can be used to calculate electrical conductivity as well as the electrons' contribution to the heat capacity and heat conductivity of metals.
  • Metals are ductile -- capable of plastic deformation. Hooke's law describes reversible elastic deformation in metals, in which the stress is linearly proportional to the strain. Forces larger than the elastic limit, or heat, may cause an irreversible deformation of the object.
  • In general, metals are denser than nonmetals. This is due to the tightly packed crystal lattice of the metallic structure. The large amounts of delocalized electrons, the tighter the metallic bonds are.
  • metal
    Any of a number of chemical elements in the periodic table that form a metallic bond with other metal atoms; generally shiny, somewhat malleable and hard, often a conductor of heat and electricity
  • metallic bond
    a chemical bond in which mobile electrons are shared over many nuclei; this leads to electrical conduction

Examples

  • Although metals are black due to their ability to absorb all wavelengths equally, gold has a distinctive color. Due to the theory of special relativity, increased mass of inner-shell electrons that have very high momentum causes orbitals to contract. Because outer electrons are less affected, blue-light absorption is increased, resulting in enhanced reflection of yellow and red light.Figure 0


Activity lists metals and
hydrogen, in order of reactivity;
any element in the series will displace
ions of an element below it from an
aqueous solution.




Lithium
Potassium
Barium
Calcium
Sodium
These metals displace hydrogen from water

Lead will displace hydrogen from
an acid, while copper does not.
Metal very high in the activity
series are very reactive and will
displace hydrogen from both
water and an acid.





Magnesium
Aluminum
Zinc
Iron
Nickel
Tin
Lead



These metals displace hydrogen from acids

Hydrogen



Copper
Mercury
Silver
Gold
These metals do not displace hydrogen from acids or water




ACTIVITY SERIES OF HALOGENS



A Halogen can also displace another halogen



Fluorine
Chlorine
Bromine
Iodine
A specific halogen can displace any halide ion that appears below it