Inorganic chemistry mainly involves the study of objects of the mineral kingdom, as opposed to organic chemistry, which obviously deals with organic compounds. Despite the privative prefix seemingly defining as inorganic that which does not retain what is organic, there is no clear demarcation between these two fields of chemistry. As many compounds fall at the boundary between the two fields, there is no clear-cut division between them.

This division can be illustrated as follows: galleries dug by science in the knowledge reservoir throughout its decades-long progress have followed various lodes, and have come to converge despite their starting point being located in distinct areas of knowledge. This may be the characteristic of various branches of chemistry that have converged over time.

According to the most general definition, inorganic chemistry relates to all non-organic compounds formed of elements that compose the periodic table.

One part of this domain may be represented as a list of structures and their corresponding properties, as well as their chemical reactivity, applications and methods used to obtain the elements and their simplest or most complex derivatives.

With this perspective in mind, a presentation can be elaborated depending on the interest that the compounds present for the branch of chemistry practiced by the author. Moreover, presenting all these elements and everything related to them is always a challenge, since, on the one hand, it is difficult to elaborate an exhaustive presentation, which would come down to plagiarizing encyclopedias, and, on the other hand, it is equally difficult to draw clear limits.

Many books offer these rich and exciting descriptions that make us love chemistry [ANG 07], but this type of description is beyond the scope of the present book.

Given the availability of reliable and comprehensive databases, such as the Handbook of Chemistry and Physics [HAY 15], which should always be within our reach, this type of inventory will be omitted here. Moreover, for consistency reasons, that particular work has been used as a source for most of the data in the present book.

Since one of the objectives of this book is to propose easy-to-find and reliable data, links to well-known sites and easy-to-consult files, all accessible to the scientific community, will be provided.

VESTA (Visualization for Electronic and Structural Analysis) software has been used for the design of this book, since high quality representation and drawing of the most representative figures may prove to be difficult in the absence of a high performance tool [MOM 11].

All the structures referred to in this book have been taken from Crystallography Open Database (http://www.crystallography.net/), a comprehensive resource featuring over 376 000 entries. A number of these structures can be found in the Handbook [HAY 15], in various books or publications, or in other databases that have been consulted for data consolidation purposes.

A brief history reveals that the most ancient branch of inorganic chemistry is unquestionably metallurgy, whose practice dates back to 2500 BC, and is attributed to Egyptians. Indeed, they practiced mining while Europe was in the Bronze Age and Europe’s inhabitants began ore mining and processing, making copper and tin alloys.

The Bronze Age was an essential period marked by the use of metals and, above all, by the development of metallurgy and thus the development of the techniques needed for obtaining bronze (an alloy of copper and tin).

Metallurgy is the study of metals: their extraction, properties and processing. By extension, it is also the name given to the industry producing metals and alloys, which relies on the mastering of this science. This emerging metallurgy required expertise in the art of fire, which was acquired by pottery firing. Extraction of metal from ores depends on the mastering of high-temperature furnaces as copper melts at 1085 °C, though the melting point can be significantly reduced by the addition of tin. Subsequent to copper metallurgy, iron metallurgy requires a higher temperature as iron melts at 1538 °C, which explains the chronology of the bronze and iron ages.

The wealth of empirical knowledge acquired and transmitted gave rise to alchemy, whose fantasies, still present in the collective unconscious, are often associated with chemistry. The best example is the philosopher’s stone, which allows for metal transmutation (turning lead into gold, obviously), but alchemists have gone even further and have imagined the panacea (universal remedy), as well as the elixir of life, which nowadays has taken the more mundane name of brandy.

Chemistry as we know it started with the creation of the periodic table, and Lavoisier can be considered its founding father, as he is one of the first experimental chemists.

Referring to the practice and definition of chemistry, Lavoisier stated the following:

“As the usefulness and accuracy of chemistry depends entirely upon the determination of the weights of the ingredients and products both before and after experiments, too much precision cannot be employed in this part of the subject; and, for this purpose, we must be provided with good instruments. As we are often obliged, in chemical processes, to ascertain, within a grain or less, the tare or weight of large and heavy instruments, we must have beams made with peculiar niceness by accurate workmen… I have three sets, of different sizes…

The principle object of chemical experiments is to decompose natural bodies, so as separately to examine the different substances which enter into their composition.” (Antoine-Laurent de Lavoisier, Elements of Chemistry, 1789)

These several phrases render both the essential concept, the fact that chemistry is first of all an experimental science, and the fundamental concept, the fact that chemical substances can be decomposed into simple substances. These two notions will lead to the elaboration of the periodic table.

The periodic table has not historically allowed for an explanation of the properties of elements, since it has been in existence for one century, should Moseley be considered the scientist who completed the work. The reverse has actually been the case, as experimentally determined properties of the elements have helped the community of chemists in the 17th Century in the step-by-step building of this currently omnipresent classification.

Inorganic chemistry is the intersection of many branches of chemistry, and this field often leads to crystals and to an understanding of their packing, which may be more or less complex, but is always surprising. Moreover, the set of elements presented in this book should facilitate the comprehension of the structure of perfect crystals (defects will not be covered).

It is thanks to the use of the periodic table, knowledge of the nature of bonds, notions of symmetry and comprehension of binary phase diagrams that crystals are perceived as less enigmatic.

The purpose of this book is to empirically present, based on observations, the structures of the main crystal compounds and to rely on the periodic table for a better comprehension of their structure, linking it whenever possible to the properties of these crystals.

We have therefore opted for a structure in which chapters can be read randomly, the only guide being a need to access data, a desire to immerse oneself once again in a field of knowledge or the opportunity to compare one’s knowledge with that presented in the book. This information will be rooted in observations and will be presented in a more empirical rather than theoretical manner, being accompanied by examples and representations that help in visualizing the properties described.

The first chapter presents a reading of the periodic table that relies on the characteristics of atoms and ions (electronegativity, ionization potential, electron binding energy, etc.). It should contribute to an overall original perspective on the periodic table by providing simple and efficient reading keys.

The second chapter develops the bases of crystallography starting from empirical observations and analyses of the structure of metals. It closes with a description of binary phase diagrams that allows the association of structures with properties and offers basic knowledge of metallurgy.

The third chapter offers a presentation of typical crystals depending on the complexity of their chemical formula and of their packing. The study focuses on MX-type binary crystals (CsCl, NaCl, ZnS sphalerite and wurtzite and NiAs) and then on MX₂-type crystals (CaCl₂, Li₂O, TiO₂, CdI₂ and CdCl₂) by means of representations offering descriptions in a simple manner. Finally, it presents ternary perovskite crystals (SrTiO₃) and spinel (MgAl₂O₄).

Visual memory is strongly involved and notions such as ionicity or space availability facilitate a simple and effective approach to the structure and nature of bonds in crystals.