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

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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

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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 additional 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.

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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 electrical 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. but they are nevertheless more reac- tungsten. • They form di- and trivalent tive than the less typical metals. They form coordination com- compounds. They share the following properties: pounds with ammonia, e.g., the • They form carbonyls with They resemble each other ammines of cobalt and nickel. CO. quite closely besides showing They mostly form borides, car- • All three metals have nearly the usual group relationships bides, nitrides, and hydrides, the same melting point (about because they have the same which have mostly metallic 1500 °C). number of the outermost elec- character. • All three metals occur in trons. They have the lowest solubility nature together in the native They may lose additional elec- in mercury. state in the minerals awariait,

trons from the next lower shell The transition metals can be divided Fe(Ni,Co)3, and josephinite, to form ions with higher charg- into three groups: Fe(Ni,Co)2. es. As a result they show a Vertical transition metals. Horizontal-vertical transition variable valence. For example, These are the vertical groups metals. This is the platinum vanadium exists in +2, +3, +4, scandium to manganese. They metals group where the similar- and +5 oxidation states, and show similarity in the vertical ity between the six metals is titanium in +2, +3, and +4. direction, e.g., Zr-Hf, Nb-Ta, in the horizontal and vertical The atomic radius of the suc- and Mo-W. The group Sc, direction. cessive metals in a certain Y, La, and Ac form colorless • They resist corrosion. horizontal period decreases compounds and have the same • They occur together in nature slightly as the atomic number valency (+3). in the native state. rises because when an electron Horizontal transition metal. is added to an inner shell it This is the group iron, cobalt, Inner transition metals decreases slightly the size of and nickel. They show similar- the atom as a result of increased ity in the horizontal direction. These metals have the same number electrostatic attraction. • All three metals are ferro- of electrons in the two outermost Most of them form colored ions magnetic. shells but a progressively greater in solution due to electronic • Their carbides have inter- number of electrons in the next inner transition with the exception of mediate properties between shell. They form two groups: the group Sc, Y, La and Ac that the metal-like character of The lanthanides These are the metals between lanthanum and hafnium, namely cerium to lutenium. Although they have two electrons in the outermost shell, and one would expect that they would form divalent compounds, yet their most common valency state is three. This is one of the exceptions in the Periodic Table. Beside showing multiple valency they also form colored ions in solution (Table 4). Being less reactive than the typical metals, they are so similar in chemical properties that their separations is usually done by Table 3: Colour of transition metal ions in solution. Incomplete list making use of differences in because many compounds are insoluble or when soluble, hydrolyse physical properties. and precipitate They form ionic carbides that decompose with water liberat-

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While plutonium shows similarity to samarium, thorium and uranium differ much more than do cerium and neodym- ium. While thorium is like cerium in the tetravalent state, uranium is most stable in the hexavalent state. Thus they are, in this respect, more like transition metals than lanthanides. Plutonium is most stable in the tetravalent state, but also occurs Table 4: Colour of inner transition metal ions in solution in the +3 and +6 valent states. Americium and curium do show similarity and difficulty of sepa- ing hydrogen. However, these ration comparable to the lan- The actinides carbides have some metal like thanides. character, e.g., they have metal- These are the metals following actin- lic luster and electrical conduc- ium, namely thorium to lawrencium. Discussion tivity. Of this only thorium, uranium, and As in typical and transition plutonium are of practical impor- Since its inception in 1869 by Men- metals, the atomic radius in the tance. In this group the 6d and 5f deleev, the Periodic Table has under- lanthanides gradually decreases energy levels of electrons may be too gone numerous changes (Table 5) and from lanthanum to lutetium close to each other which results in a large number of forms have been with the result that although cases where f-levels may be occupied proposed. in one atom but not in another. Ura- nium has multiple valency (+ 3, +4, IUPAC‘s Periodic Table +5, and +6) and form colored compounds; plutonium exists in +3 and In 1985 the International Union of +4 oxidation states and also forms Pure and Applied Chemistry (IUPAC) colored compounds (Table 4). recommended that the groups in the The actinides differ from the Periodic Table should be numbered lanthanides by the fact that they from 1 to 18, i.e., the alkali metals can be readily separated one are Group 1 and the inert gases are from the other by differences Group 18 [1, 2]. This numbering in the chemical properties while was a compromise between the North this is not the case with the lan- American and the European Periodic thanides. Tables (Fig. 5). But this raised a hot They are similar to the lantha- debate among chemists that was nides in forming ionic carbides published in Chemical & Engineer- with some metal-like behav- ing News in a series of letters to ior that decompose with water the editor [3-5]. Almost all these yielding hydrogen. letters opposed the new number- Fig. 4: Lanthanide Contraction

1869 Mendeleev Table based on atomic weight the atomic radius of lanthanum 1898 Crookes Position for the inert gases is larger than that of yttrium, which is above it in the Table, 1913 Moseley Table based on atomic number; positions of argon and potassium, cobalt and nickel, and tellurium and the atomic radius of lutetium iodine exchanged is smaller that of yttrium, i.e., La, Y, Lu. This is known as the 1922 Bohr Table based on electron shells; the term transition metals introduced; position for the lanthanides „lanthanide contraction“ and is established responsible for the fact that the atomic radii of the metals lan- 1945 Seaborg Position for the actinides thanum to mercury are nearly identical to those above them in Table 5: Major developments in the Periodic Table the Table (Fig. 4).

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The position of aluminum

Moving aluminum further away from gallium with which it occurs in baux- ite may raise objection. However, it should be recalled that there are marked differences between both metals: While aluminum oxidizes so rapidly that it soon forms a non- porous protective layer, gallium does not. Gallium can be electrodeposited from aqueous solution, while aluminum cannot.

Al(OH)3 does not dissolve in ammonium hydroxide solution,

but Ga(OH)3, does dissolve. Gallium is precipitated from

aqueous solution by H2S as a Fig. 5: Different Numbering of the Groups in the Periodic Table sulfide; aluminum does not. Aluminum forms carbides, gal- ing system. It is believed that this tion) is in fact composed of lium does not. conflict may be resolved if chemists three different groups: boron Aluminum carbide, Al4C3 is and physicists abandon the old idea is a metalloid, aluminum is a similar to the carbides of the of numbering the groups. Instead, typical metal, gallium, indium, first three groups, being ionic it would be more reasonable to give and thallium are less typical colorless compound containing 2- names to each group of the elements metals. the C2 anion that decompos- that reflect their electronic structure, The group starting with carbon es in water. However, it liber- the nature of their bonding, and their and ending with lead (Group 14 ates methane instead of acety- properties (both physical and chemi- of the IUPAC notation) is again lene like the other members of cal). These names should be easier composed of three different the group: Al4C3 + 12 H2O → for students to remember and give groups: Carbon is a nonmetal; 4 Al(OH)3 + 3 CH4 them a deeper understanding of the silicon and germanium are met- Gallium forms a gaseous hybride,

Periodic Table. alloids while tin and lead are Ga2H6, while aluminum forms The present classification in ten less typical metals. a white solid polymer hydride, groups (Fig. 6) should be helpful in The diagonal relationship (AlH3)x this respect. In this classification between Li – Mg, Be – Al, and Historically, aluminum oxide aluminum is moved to a position B – Si can readily be demon- was considered an earth like the immediately next to magnesium so strated by the arrows connect- rare earths and it fits with the that the alkali metals, the alkaline ing each two elements. scandium group. earth metals, and aluminum form a There is a little advantage in keeping Mendeleev successfully predict- group of typical metals. The other these two groups as Groups 13 and ed the properties of scandium groups are: the less typical met- 14 (or III A and IVA) - they have before it was discovered by link- als, the vertical transition metals, little in common. There is a great ing it with aluminum. the horizontal transition metals, the disparity in the melting points of the The chemistry of scandium is vertical-horizontal transition metals, members of both groups. Similarly, very similar to that of aluminum the inner transition metals (the lan- the nitrogen and oxygen groups and the ions Al3+, Sc3+, Y3+, La3+, thanides and the actinides), the met- are a mixture of nonmetals and and Ac3+ form a series similar to alloids, the monatomic nonmetals, metalloids; the differences are more Mg2+, Ca2+, Sr2+, Ba2+ and Ra2+. and the covalent bond nonmetals. than the similarities. It would be Gallium is a typical dispersed An advantage of this classification advantageous to make this distinc- element whose relative abun- would be putting each member of tion. It would also be advantageous dance in the Earth‘s crust is a group in its logical position. For to identify the Ti, V. Cr, Mn, Fe, Co, 1.5 x 10-3%, aluminum is the example: and Ni as a group with a horizontal third most abundant element The group starting with boron similarity, and the platinum metals with a relative abundance of and ending with thallium as another group with both horizon- 8.13% (after oxygen and sili- (Group 13 of the IUPAC nota- tal and vertical similarities. con).

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Another objection, which may arise from this transfer, is the dissimilar- ity of the electron orbital structure of aluminum as compared to Sc, Y and La: aluminum has 2s and 1p electrons, while the others have 2s and 1d electrons. This objection can be answered in the following. The classification of the elements in the Periodic Table according to the popu- lation of electrons in the subshells, i.e., as s-, p-, d, and f-block elements does not indicate or explain many facts such as: The boron group elements are in the p-block but show different chemical and physical Fig. 5: Different Numbering of the Groups in the Periodic Table properties, e.g., boron is a metalloid while the other elements tum mechanical considerations. Inner transition metals: are metals. Further, the struc- For example: • The lanthanides ture of boron hydroxide (boric • Chromium and manganese, • The actinides acid) is fundamentally different and molybdenum and techne- An advantage of this classification from aluminum hydroxide. In tium have the same number would be putting each member of a the former no oxygen atoms of d-electrons and different group in its logical position.

are shared between the M(OH)n numbers of s-electrons instead coordination groups in contrast of the reverse. References to the latter. • Europium and gadolinium Boron group elements have have similar f- and differ- - Anonymous, “Group Notation Revised in Periodic Table”, Chem. & Eng. News, three electrons in their outer ent d-electrons instead of the February 4, 1985 pp. 26-27 shell: 2s and 1p. However, all reverse. - R.L. Rawls, “Revisions to Periodic Table three electrons are lost in one This renders the strict adherence to Sparks Controversy”, Chem. & Eng. step except thallium and to a the s-p-d, and f-classification point- News, January 27, 1986 pp. 22-24 - Letters to the Editor, Chem. & Eng. minor extent gallium. On the less, and it should be better to con- News 1985: February 25 pp. 4-5, March other hand the scandium group sider the total number of electrons in 11 pp. 4-5, March 18 p. 2, April 8 p. 5, elements have also three elec- a shell. It should also be noted that April 22 p. 87, May 6 pp. 5 and 46, May trons in their outer shell: 2s and this classification was introduced by 13 pp. 2 and 36, June 10 p. 4, August 5, pp. 4 and 47, August 12 pp. 2-3, August 1 d, and all three are lost in one physicists who are not necessarily 19 p. 3 step. Hence the distinction in interested in chemical properties. - Letters to the Editor, Chem. & Eng. electron orbital is not a critical News 1986 January 27 p. 22, March 3 criterion for classification of pp 3 and 46, March 17 p. 3, April 14 pp. Conclusions 3 and 67, April 28 pp. 2 and 90, May 19 the elements, and it is the total p. 2, June 23 p. 4, June 30 pp. 2 and 47, number of electrons that should It is suggested that chemists abandon September 1 pp. 2-3, November 10 pp. be taken into consideration. the old tradition of numbering the 2 and 39 The copper and zinc groups groups in the Periodic Table, and to - Letters to the Editor, Chem. & Eng. News 1987 January 12 pp 3, 24, and 46, of elements are in the d-block give the following descriptive names February 2 p. 3, April 6 p. 41 which is used to be known as instead: - F. Habashi, Metals from Ores. An Intro- transition metals but differ from Monatomic nonmetals duction to Extractive Metallurgy, Mé- tallurgie Extractive Québec, Sainte-Foy, the other members of the same Covalent nonmetals Québec City 2003; distributed by Laval block in that the atomic radius Metalloids University Bookstore increases with atomic number Typical metals whereas in the other members it Less typical metals is the opposite. As a result they Transition metals with vertical have different chemical proper- similarity (1) Fathi Habashi, Department of ties and should not be included Transition metals with horizon- Mining, Metallurgical, and Mate- in the transition metals group. tal similarity (Ti to Ni) rials Engineering, Laval Univer- There are many irregularities in Transition metals with vertical sity, Quebec City, Canada G1V the electron orbitals in the sub- and horizontal similarity (plati- 0A6, Fathi.Habashi@@arul. shells, which arises from quan- num group metals) ulaval.ca

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