Structural Chemistry of Silicates Ratio of ionic radii: Each cation is surrounded by a coordination polyeder The distance between cation and anion is determined by the sum of the ion radi, the coordination number by the ratio of the radii
Role of cations in silicate mineral structure Coordination Number: The number of oxygen atoms surrounding a cation is called its coordination number This is a key factor in determining the mineral's structure
NAME NAME_____________________ - University of Massachusetts Lowell Isodesmic – bond strengths are the same throughout the crystal structure Anisodesmic – bond strengths inside of one type of polyhedral in a strurcture are different from that of other bonds in the structure Mesodesmic – e v number is equal to 1⁄2 the valence number of the anion
What is coordination number (CN) in silicate minerals? Name three . . . Name three crystallographic sites in silicates and indicate their CN | KnowledgeBoat Get ICSE CBSE textbook solutions of all subjects with video explanations Do practice tests get your doubts cleared instantly by best teachers
Silicate Structures, Neso- Cyclo-, and Soro- Silicates Larger ions like Ca +2, and Na +1, are found in octahedral coordination or 8-fold, cubic coordination sites Very large cations like K +1, Ba +2, and sometimes Na +1 are coordinated by 12 oxygens in 12-fold coordination sites
13. 2. 2: Coordination Number - Geosciences LibreTexts The number of anions to which some particular cation bonds is the cation’s coordination number (C N ) Si 4+, for example, nearly always bonds to four O 2- anions in minerals, and therefore has a C N of 4
Coordination Number: Definition and Examples - Chemistry Learner The coordination number in a complex molecule or crystal is the number of atoms, ions, or molecules bonded to the central atom The ion or molecule surrounding the central atom is called a ligand
Microsoft PowerPoint - Silicate_Minerals Several structure types are possible – in the silicate structures the letter A = non-silicon cations with lower valency then Si4+ , B = Si or Al or other higher valent cations, O = oxygen