Question

The structure of $ MgO $ is similar to $ NaCl $ . What is the coordination number of $ Mg $ ?

Answer 1

Hint : A lattice structure is a space-filling unit cell that can be tessellated along any axis with no gaps between cells. These structures are an emerging solution to weight, energy and advanced manufacturing time reduction. To date, there is no compilation of literature or state-of-the-art reviews in the lattice structure field due to their prevalence across a wide range of research areas. A systematic review would therefore aid in identifying the wide scope of lattice structure design and applications.

Complete Step By Step Answer:
NaCl has a cubic unit cell. It is best thought of as a face-centered cubic array of anions with an interpenetrating fcc cation lattice (or vice-versa). The cell looks the same whether you start with anions or cations on the corners. Each ion is 6-coordinate and has a local octahedral geometry. MgO crystallizes in a cubic cell with a rock-salt structure. The crystal structure can be described as a fcc lattice of Mg ions with O ions occupying all the octahedral holes or vice versa. The rock-salt structure is the most common for MX compounds.MgO is an important oxidic system in minerals, in defective systems as well as in adsorption phenomena. Therefore, despite its simplicity, MgO has been the subject of many research studies. $ MgO $ has $ NaCl $ type structure of ions. Let us first understand the concept of coordination number. The coordination number is the number of ions that immediately surround an ion of the opposite charge within a crystal lattice. For sodium chloride, there are 6 anions around each cation (coordination number of $ Na $ =6) because of the 1:1 stoichiometry, there must also be 6 cations around each $ C{l^ - } $ ion.Similarly, $ M{g^{2 + }} $ and $ {O^{2 - }} $ also has the octahedral structure and follows NaCl type geometry. Therefore, the coordination number of Mg is also 6.

Note :
Students must find it very interesting that often the color of a compound is affected by the specific materials coordinated to that central ion. Always find the coordination number with respect to the central metal ion , not by the surrounded ions .