Electron Configuration
Aluminum atoms have a peripheral electron configuration of 3s2 3p1 and often appear in the plus 3 oxidation state in compounds. Aluminum atoms have empty 3d orbitals that, when given electron pairs, can form stable complexes with coordination numbers of 6 or 4. An aluminum atom gives a trivalent aluminum ion if it simultaneously loses two 3s electrons and one 3p electron; if one 3s and one 3p electron are lost, the divalent ion is produced; if one 3p electron is lost, a univalent ion results. Low-valent aluminum ions are usually unstable at low temperatures.
Crystal Lattice
The lattice of aluminum belongs to the face-centered cubic type. Aluminum atoms are located on the nodes of the lattice and in the center of the faces, equivalent to 4 aluminum atoms in each unit cell. The face-centered cubic structure has close-packed slip planes that give aluminum its excellent ductility and formability.
Physical Properties from the Structure
The metallic bonding and FCC lattice give aluminum high electrical and thermal conductivity, second among common metals only to copper per unit volume. The low density of 2.70 g per cubic centimeter comes from the low atomic weight of 26.98 combined with the open FCC packing efficiency. The melting point is about 660 degrees C, and the coefficient of thermal expansion is moderate, supporting welded and fastened structures.
Why the Structure Matters in Applications
The FCC structure supports deep drawing, rolling to thin foil, and extrusion into complex profiles without cracking. The metallic bond and free electrons provide the reflectivity used in lighting and thermal insulation, and the stable oxide layer formed by the valence electrons protects the metal from corrosion.
Frequently Asked Questions
Q: What is the electron configuration of aluminum?
3s2 3p1.
Q: What oxidation state is most common?
Plus 3.
Q: What is the crystal structure?
Face-centered cubic with 4 atoms per unit cell.
Q: Why is aluminum ductile?
The FCC lattice has close-packed slip planes.
Q: What is the melting point?
About 660 degrees C.
Q: Why is aluminum conductive?
Metallic bonding with free electrons.
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