1. Metals - Bonding and Crystal Structure

2. Metallic Bonding Formed between atoms of metallic elements
Good conductors of heat and electricity, lustrous, relatively high melting points, malleable and ductile.
Examples; Na, Fe, Al, Au, Co

3. Structure of Metals
Metals have low EN – they lose their valence electron(s) easily
Become positively charged kernels.
Metallic crystal structures are a frame of kernels.
The electrons from each metallic atom are found in a common pool or “sea” and are free to move between all the kernels.
They are called delocalized electrons.

4. Metallic Bonding - A Sea of Delocalized Electrons

5. Crystal Structures Metal kernals are viewed as hard spheres
The packing pattern adopted depends on the size of the kernel and the number of e- s released into the sea.
The metal bonding strength follows Coulomb’s Law -
The smaller the kernel and a larger number of released e- s means a stronger bond.

6. Packing types Body Centered 8 nearest neighbors.
68% packing efficiency
Alkali metals pack this way, most malleable, softest
Close Packed
-Hexagonal cubic
-Face centered cubic
12 nearest neighbors.

7. Hexagonal Close Packing
Alternating planes of hcp spheres
Those in the 3rd plane pack directly above those in the 1st plane – ABA pattern
74% of the space is filled by metal kernels, the rest is filled by electrons.
used by Be, Co, Mg, Zn, Sc, Ti, Cd & Zr
Least malleable packing, hardest

8. Face Centered Packing
Identical to hexagonal packing, EXCEPT the 3rd spheres are in the holes that were not used to form the 2nd plane
The 4th plane is above the 1st plane – ABCA
Used for Ag, Al, Au, Ca, Cu, Ni, Pb and Pt
More malleable than hexagonal, softer

9. Close Packing

10. Alloys Alloys are solid solutions of metals.
They are usually prepared by mixing molten components.
They may be homogeneous, with a uniform distribution, or occur in a fixed ratio, as in a compound with a specific internal structure.

11. Substitutional Alloys
Substitutional alloys have a structure in which sites of the solvent metal are occupied by solute metal atoms.
An example is brass, an alloy of zinc and copper.

12. Interstitial Alloys
Interstitial alloys are solid solutions in which the solute atoms occupy holes (interstices) within the solvent metal structure.
An example is steel, an alloy of iron and carbon.