provoc~tive opinion The Periodic Table-A
New Arrangement
Michael L a b University of Natal, Durban, South Africa 4001 prediction has proved to be the case; the element is promethium, atomic number 61. The diagonal relationships hetween Be and Al, and Al and Ti, as well as between Li, Mg, and Sc are also quite obvious. (These relationships certainly are not evident in the standard long form, no matter what system of labelling is used). The laree eaD - . above Fe.. Co.. and Ni em~hasizestheir uniqueness as transition metals, triads in the sense used by Mendeleveff. One can also see the oossibilitv of isostructural compo&ds for the pairs silicon A d titaniim (e.g., the liquids Sic14 and TiClJ, phosphorus and vanadium (e.g., POCI3 and VOCI3), sulfur and chromium (e.g., SO:- and Cr0:-), and chlorine and manganese (e.g., C1207 and MnnOd. This simple expediency of duplicating the location of the elements certainlv makes it easier to see the familial relationships. 1 am sure that there will be those who disapprove of what I have done. hut I have found that this design has the merit of being usefh for teaching inorganic chemis&y. After all is said and done, the purpose of the periodic table is to show kinships; and this arrangement does just that.
Over the past five years there has been much debate about how to label the periodic table so as best to indicate the relationships between subgroups. For example, are Mg and Zn to be in groups labelled IIA, IIB; 2A, 2B; 2,12; 11, XII; or something else? What is offered here is a new layout of the periodic table' that is a compromise encompassing both the current long form and the older short form (see figure). The first two short periods (Li to F and Na to C1) are duplicated. Also, the elements 89 to 92 (Ac to U)are continued across under elements 57 to 74 (La to W), thus emphasizing the tetra-valencv of thorium. The lanthanides and actinides are separated(= usual), hut they have been carefullv lined uo verticallv so that Ce falls below Th, and Pm (61) below TC (43j. I arranged the elements in this way because I wanted to emphasize the important subgroup relationships and to make it simple to obtain the maximum amount of chemical information from a glance at the periodic table. This layout has the advantage of the original short Mendeleyeff form, which shows beautifully the vertical links between magnesium and zinc, as well as between scandium and aluminum; that uranium can be expected to have an oxidation state of +6; that cerium might have oxidation state +4; and that the element following barium and falling below number 43 (technetium) might also be radioactive. This last-mentioned
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' S. Afric. J. Sckma, 1986, 82, 340 ((editorial).
The Chemical Elements
'
67
68
59
SO
61
82
BS
84
65
BB
87
68
69
70
n
Lanthanides La Ce Pr Nd Pm Sm Eu G d Tb Dy Ho 'Er Tm Yb Lu 89
90
91
92
91
94
88
BB
97
98
Actinides Ac Th Pa U Np pu AmCm Bk Cf 746
Journal of Chemical Education
99
100
101
102
103
Es Fm Md No Lw
