THE PERIODIC TABLE and the METALLURGIST Fathi Habashi

Laval University From the SelectedWorks of Fathi Habashi June, 2008 THE PERIODIC TABLE AND THE METALLURGIST Fathi Habashi Available at: https://works.bepress.com/fathi_habashi/79/ Metall-Forschung The periodic table and the metallurgist Habashi, F. (1) As science advances, its laws become fewer but solid elements carbon, They are reactive, i.e., react of greater scope. In this respect the Periodic sulfur, phosphorus, readily with water and oxy- Law, which is the basis of the Periodic Table, and iodine. These ele- gen. The driving force for this represents a major step in the progress of chem- ments do not have the reactivity is the inclination to istry - it affords the natural classification of the properties of a metal. achieve maximum stability by elements. The Periodic Table was developed by Nonmetals except attaining the electronic struc- chemists more than one hundred years ago as the inert gases read- ture of an inert gas. A reac- a correlation for the properties of the elements. ily share electrons. tive metal such as aluminum or With the discovery of the internal structure of Their atoms are unit- magnesium may be used as a the atom, it became recognized by physicists as a ed together by cova- material of construction because natural law. When the crystalline structure of sol- lent bond, i.e., atoms of the protective oxide film that that share their outer is formed rapidly on its surface. ids was studied, the nature of the chemical bonds electrons. They often They form only colorless com- was understood, and the theory of metals was put form diatomic mol- pounds. forward, it became an essential tool not only for ecules such as H2, Cl2, Within a certain vertical group chemists and physicists, but for metallurgists as N2 or larger molecules the atomic radius increases well. Of the 87 naturally occurring elements, 63, such as P4 and S6, or with increasing atomic number i.e., about three fourth are described as metals, giant molecules, i.e. a because of the added electron 16 as nonmetals, and 9 as metalloids. It is sug- network of atoms of shells. gested that chemists abandon the old tradition of indefinitely large vol- Within a certain vertical group numbering the groups in the Periodic Table, and ume such as carbon the reactivity increases with to give descriptive names instead. in form of graphite or increasing atomic number diamond. because of the ease with which etals are the most common Metalloids have covalent bond like the outermost electrons will be articles in everyday life; nonmetals, but have intermedi- lost since they are further away Mthey are usually used in ate properties between metals and from the nucleus. Thus cesium form of alloys, which are a combina- nonmetals. Table 1 summarizes the is more reactive than rubidium, tion of two or more metals. They properties of metals, nonmetals, and and rubidium more than potas- are the basis of the metallurgical metalloids. sium, etc. industry. Nonmetals, except carbon, With increasing charge on the are hardly used by an average person. Classification of Metals nucleus, the electrostatic attrac- Air, a mixture of nonmetals is known tion for the electrons increases to exist but is not seen by people. Since metals are those elements capa- and the outermost electrons will Nonmetals are the basis of the chemi- ble of losing electrons, therefore, not be easily lost hence the cal industry. Metalloids are the basis they can be divided into typical, less of advanced technology and the elec- typical, transition, and inner transi- tronics industry (Fig. 1). In the solid tion. This division is a result of their state metals are composed of crystals electronic structure (Fig. 2). made of closely packed atoms whose outer electrons are so loosely held Typical metals that they are free to move through- out the crystal lattice. This structure These are the alkali metals, the alka- explains their mechanical, physical, line earths, and aluminum. They have and chemical properties. the following characteristics: Nonmetals include the inert gases1, They have an electronic struc- hydrogen, oxygen, nitrogen, fluorine, ture similar to that of the inert and chlorine, liquid bromine, and the gases with one, two, or three 1 Inert gases are a historical name for the group electrons in the outermost shell. of gases starting with helium and ending with They have single valency, i.e., radon. They were until the 1960‘s considered inert when few compounds of xenon with they lose their outermost elec- Fig. 1: Metals, nonmetals, and fluorine were prepared. trons in a single step. materials 454 · 62. Jahrgang · 7-8/2008 Metallurgie Table 1: General characteristics of metals, metalloids, and nonmetals reactivity decreases. Thus mag- to four electrons and the next inner a result of their electronic configura- nesium is less reactive than shell contains 18 instead of 8 elec- tion they are characterized by the sodium, calcium less than potas- trons as in the inert gas structure. As following: sium, and so on. With increased electrostatic attraction for the electrons as a result of increasing charge on the nucleus, the size of the atom decreases. Thus, aluminum has a smaller radius than magnesium, and magnesium smaller than sodium. With decreased radius and increased atomic weight the atom becomes more compact, i.e. the density increases. Thus, aluminum has higher density than magnesium, and magnesium higher than sodium. They have appreciable solubility in mercury and form compounds with it except beryllium and aluminum. Less typical metals These metals are: copper, silver, gold, zinc, cadmium, mercury, gallium, indium, thallium, tin, and lead. They differ from the typical metals in that they do not have an electronic structure similar to the inert gases; the outermost shell may contain up Fig. 2: Electronic Configuration of the Elements · 62. Jahrgang · 7-8/2008 455 Metall-Forschung radius these metals are more dense than their corresponding typical metals. Some of these metals show two different valency states, e.g., copper as CuI and CuII, gold as AuI and AuIII, mercury as HgI and HgII, tin as SnII and SnIV, and lead as PbII and PbIV. This is because of the possibility of removing one or two electrons from the 18-electron shell. Few of these metals from colored ions in solution, e.g., CuII and AuIII, or colored compounds, e.g., copper sulfate pentahydrate (blue), cadmium sulfide (yellow), etc. (Table 2). This is due to the possibility of movement of electrons from the 18 electrons shell to a higher level. Fig. 3: Atomic Volume of the Elements They have the highest solubility in mercury since their electronic structure is similar as that The atomic radius is less than shell and that shell, and also of mercury. Also, they do not the corresponding typical met- the increased repulsion between form compound with mercury. als in the same horizontal group the electrons themselves in that because the presence of 18 elec- shell. Transition metals trons in one shell results in an The outermost electrons will not increased electrostatic attrac- be easily lost, i.e. these metals These are the metals in the verti- tion with the nucleus. Thus, are less reactive than their cor- cal groups in the Periodic Table the atomic radius of copper is responding typical metals for from scandium to nickel. They not less than potassium, silver less two reasons: only have electronic configuration than rubidium, and gold less • There is no driving force to different from the inert gases but than cesium. However, the lose electrons since an inert they are characterized by having the atomic radius increases with gas electronic structure will same number of electrons in their increased number of electrons not be achieved. outermost shell and a progressively in the outermost shell (which • There is a stronger electro- greater number of electrons in the is contrary to the typical met- static attraction due to the next inner shell. There are, however, als), i.e. the atomic radius of smaller atomic radius as some apparent irregularities in the gallium is larger than that of compared to that of the typi- number of electrons in the outer- zinc, and zinc is larger than cal metals. most electron shells. This is due to copper. This is demonstrated in Because of the higher atomic energy levels, which are determined Figure 3: The atomic volume2 weight and the smaller atomic from spectroscopic measurements. of the typical metals decreases with increased atomic number while the reverse is true for the less typical metals. the reason for this is the shielding effect of the 18-electron shell, the increased repulsion of the addi- tional electron in the outmost 2 Atomic volume is the volume in cubic cen- timeters occupied by one gram atomic weight of the element in the solid state. It can be used as qualitative guides to the relative volumes of the individual atoms since all gram atomic Table 2: Color of the less typical metal ions in solution weights contain the same number of atoms. 456 · 62. Jahrgang · 7-8/2008 Metallurgie As their name implies the transition form only colorless compounds the transition metals and the metals have properties between the (Table 3). ionic character of the typi- typical and less typical metals. They form many covalent com- cal metals. Thus they have They are less reactive than the typi- pounds, e.g., the carbonyls of metallic luster and electri- cal metals because they will not iron and nickel, the chlorides cally conductive, but they are achieve the inert gas structure when of titanium, and the oxyacids attacked by water and dilute they lose their outermost electrons, of chromium, molybdenum and acids.

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