Structure of inorganic compounds Flashcards
What 5 things are looked at when you look at structure?
Composition Connectivity Stereochemistry Symmetry Quantitative geometry
What is quantitive geometry?
Exact relative positions of atoms
Eg. Bond lengths, bond angles, torsion angles
What is a unit cell?
The shape of the repeat unit, obtained by connecting adjacent lattice points.
Simplest structure which can be translated to create the lattice
What is a unit cell defined by?
3 axes
What is translation symmetry?
Repetition of molecules arranged in a regular way in an effectively infinite 3D repeat pattern
What is the characteristic property of a cystalline solid state?
High degree of internal order
What symmetry is always present in crystalline solids?
Translation symmetry
What is the best unit cell?
One with the shortest sides as possible and the angles close to 90degrees
How is unit cell geometry fully described?
Giving the lengths of two sides and the angle between them in 2 dimensions
What is a lattice?
An array of regularly spaced points, which shows the repeating nature of the structure, but not the actual form of the basic repeat unit
What is a crystal structure?
The combination of the lattice and the contents of the repeat unit
What effect does inversion have on cystalline solid state?
No effect
What effect does rotation have on crystalline solid state?
May force two unit cell lengths to be equal
What effect does reflection have on crystalline solid state?
Force some angles to be 90 degrees
What are the 7 crystal systems?
Triclinic Monoclinic Orthohombic Tetragonal Trigonal Hexagonal Cubic
