djvu Natural Classification of Chemical Elements (English Edition)

Introduction

We know of slightly more than a hundred chemical elements, each characterized by particular properties. They can nonetheless be grouped into two broad categories: metals and nonmetals. Nonmetals themselves are divided into noble gases, metalloids, and elements whose properties are intermediate between those of metals and metalloids. A more thorough examination revealed, from the beginning of the 19th century, the existence of "families": those of alkali metals, alkaline earth metals, halogen metalloids, "rare earth elements," and others. After several unsuccessful attempts by chemists such as Döbereiner, Newlands, and others, Russian chemist Dmitri Ivanovich Mendeleev succeeded in 1869, by studying the physical and chemical properties of the approximately 70 elements known in his time, in discovering close relationships between the properties of elements when he arranged them in increasing order of their atomic mass.

Mendeleev noticed the "periodic" return of chemical properties, which allowed him to arrange them in a way that highlighted the "families" his predecessors had already recognized. The periodic table, revised many times since Mendeleev first created it, is truly a natural classification of chemical elements. It has always adapted wonderfully to all the modifications made necessary by advances in physics and chemistry.

In the following pages, you will find two versions that will seem quite different from this periodic table. In fact, the second table provides the same information as the first, but with greater emphasis on certain different points. In both tables, each element is represented by its chemical symbol. Thus, H represents hydrogen; He, helium; Li, lithium. The small number above the symbol represents the element's atomic number; those beside the symbol give its atomic weight. The following pages contain the "long" version of the table, with the "short" version further on. In both, the elements are arranged in increasing order of their atomic number. Each table may seem, at first glance, a bewildering array of symbols, numbers, and generic names. It will be easier to understand the table if we first study only a small part of it. Let us disregard for the moment the first two elements, hydrogen and helium. Here are the following sixteen in order: These sixteen elements begin with lithium, an active, lightweight metal. The next three elements, beryllium, Be, boron, B, and carbon, C, are all solids whose metallic properties progressively decrease: carbon is a nonmetallic element. Then we encounter the metalloids: nitrogen, N, oxygen, O, and fluorine, F, which is a gaseous, highly reactive element; finally, we arrive at neon, which is a noble gas.