Ion lattice
In chemistry and solid-state physics, an ion lattice or ion crystal is understood to be the regular spatial arrangement of anions and cations of a homogeneous substance in the solid state. The lattice structure is held together by the ionic bond . The best known examples of crystals with a cubic lattice structure are ion crystals: cesium chloride for the body-centered cubic and sodium chloride lattices ( sodium chloride ) for the face-centered cubic structure.
structure
The structure of the ion lattice depends on the one hand on the size ratio of the ions and on the other hand on the charge ratio.
| Substance name | Ratio formula | cation | Anion | coordination | Crystal system | further examples | |
|---|---|---|---|---|---|---|---|
| Sphalerite (zinc blende) zinc sulfide | ZnS | Zn 2+ | S 2− | 4: 4 | Each zinc cation is tetrahedrally surrounded by 4 sulfide anions, each sulfide anion also tetrahedrally by 4 zinc cations. | cubic | CuCl, CuBr, CuI, BeS, HgS |
| Wurtzit | ZnS | Zn 2+ | S 2− | 4: 4 | hexagonal | NH 4 F, BeO, ZnO, AgI, CdS | |
| Rutile | TiO 2 | Ti 4+ | O 2− | 3: 6 | Each titanium cation is surrounded in a distorted octahedral manner by 6 oxide ions, each oxide ion in a planar manner by 3 titanium cations. Here the bond character lies between an ionic and an atomic bond | tetragonal | SnO 2 , MgF 2 , PbO 2 , MnO 2 |
| Sodium chloride | NaCl | Na + | Cl - | 6: 6 | Each sodium cation is octahedral surrounded by 6 chloride anions, each chloride anion also octahedral by 6 sodium cations. | cubic | NaF, KF, AgF, KCl, AgCl, NH 4 Cl (above 184.3 ° C), NaBr, KBr, AgBr, NaI, KI, NaH, KH, MgO, CaO, SrO, BaO, FeO, CoO, NiO, MgS, CaS, MnS, PbS |
| Calcium fluoride ( fluorite ) | CaF 2 | Ca 2+ | F - | 4: 8 | Each calcium cation is cube-shaped by 8 fluoride ions, each fluoride ion is tetrahedrally surrounded by 4 calcium cations. | cubic | PbF 2 , BaF 2 , SrCl 2 , CdF 2 ; Antifluorite structure : Li 2 O, Na 2 O, K 2 O |
| Cesium chloride | CsCl | Cs + | Cl - | 8: 8 | cubic | NH 4 Cl (at room temperature), TiCl, CsBr, NH 4 Br, TlBr, CsI, NH 4 I, TlI | |
| Potassium nitrate | KNO 3 | K + | NO 3 - | orthorhombic | |||
| Calcite (calcite) | CaCO 3 | Ca 2+ | CO 3 2− | trigonal | |||
| Sodium chlorate | NaClO 3 | Na + | ClO 3 - | monoclinic | |||
| Copper sulfate | CuSO 4 | Cu 2+ | SO 4 2− | triclinic | |||
Special forms
- In the so-called anti-structures, e.g. B. the antifluorite structure, the position of the anions and cations are interchanged.
- Ion lattices can also contain stoichiometric amounts of small molecules in the lattice gaps (for example water of crystallization ).
- Layer lattice:
- Orthoboric acid H 3 BO 3 is a planar molecule. In the solid state, these molecules form hydrogen bonds with one another , creating a two-dimensional sheet. These sheets are stacked on top of each other. The cohesion between the layers takes place through Van der Waals interaction .
- Sandwich grid:
- With cadmium iodide CdI 2 and cadmium chloride CdCl 2 there is a cation layer between two anion layers. The forces of attraction between the layers are relatively weak. These three layers can be stacked on top of each other in two ways: ABAB… like CdI 2 , Mg (OH) 2 and PbI 2 or ABCABC… like CdCl 2 , FeCl 2 and MgCl 2 .
See also
Atomic lattice , molecular lattice , metal lattice , crystal lattice , amorphous state, lattice structure , lattice constant , lattice enthalpy
Individual evidence
- ↑ The coordination indicates how many anions surround a cation and how many cations surround an anion.