PART I

INTRODUCTORY SUPPORTIVE EVIDENCES

The Lanthanide Contraction

Central to the Circular Model of the Atom are positive and negative poles.   The polarity effects are most obvious on the elements nearest each respective pole. As elements buildup the periodic table there are characteristic trends common to neighbor elements but opposite trends in elements on the same major shell levels with opposing polarity.  Group I elements are nearest the positive pole and in that group are the most electropositive elements in the entire periodic table.  Cesium has the lowest electrical resistivity and the largest atomic dimension.

A family progression of succeedingly larger dimensions occurs in the alkali metals from Lithium (1.52A), Sodium (1.86A), Potassium (2.31A), Rubidium (2.44A), then to Cesium (2.62A) as atomic number increases. In contrast, we have Lanthanum with atomic number fifty seven just beyond Cesium fifty-five being the first in a series of rare earth elements with succeedingly smaller atomic radii and increased atomic mass with each added element.  The cause of this decrease in atomic radii has been traditionally viewed as electrons screening the positive charge on the nucleus with each succeeding element. Electrons do not completely balance the positive nuclear charge hence the electrons moving in a positive field have smaller orbits and atomic dimensions.

The Circular Model of the Atom and atomic radii dimensions suggest an alternative approach. If we take the reverse of the Cesium dimension case and somewhat similar shells, then the smallest dimensional elements are the positive paramagnetic elements attracted toward the strong end of a magnetic field or negative pole. Elements with strong paramagnetic characteristics are iron (1.26A), cobalt (1.25A), nickel (1.24A), ruthenium (1.34A), rhodium (1.34A), palladium (1.37A), osmium (1.35A), iridium (1.36A), and platinum (1.38A).  These all have relatively small atomic radii in comparison with other transitional elements.

With each succeeding rare earth element additional mass is gained in the form of nucleons and an electron.  Concurrently its position is moving farther and farther from the positive polarity area of group I elements and large dimensions, toward group VIII strong paramagnetism and small diameter atomic radii. Within this buildup there is also a change in parity which we call the flip from a positive to a negative field.  This occurs between group IV and group V elements in the periodic table.  "Lanthanum is diamagnetic and as the atomic number is increased (i.e. as the f shell gradually becomes more complete) the value of the moment increases, till we reach neodymium (60); it then suddenly drops to a small value of 1.47 with samarium..." [1]. This is exactly where the negative polarity barrier occurs. Diamagnetism drops off right after neodymium (60). "In the center of the lanthanide series there is also an electron configuration which occurs in several ions--namely that of gadolinium (64) ion with just seven electrons in the 4f level.  Terbium (65), the element following gadolinium, attains the same configuration in the Gd4+ ion; whereas europium, in the Eu2+ ion also acquires the Gd3+ core by the loss of two electrons. The gadolinium ion thus occupies a special place in the series of the lanthanides, corresponding to the place of the inert gases in the periodic table as a whole" [2]. The Circular Model of the Atom has gadolinium as filling a rare earth closed shell comparable to the inert gases.

These same principles apply also to the actinide contraction and the periodic table of elements as a whole when developed on a spherical basis. When applied to the elements, negativity is a contracting force that diminishes atomic radii.

The Circular Model of the Atom offers a more logical explanation than the current view of small mass electrons having a major impact on atomic radii.

[1] Prakash, S., 1967. Advanced Chemistry of Rare Earths. 1st American ed. New York: Chemical Publishing Co., p. 391.

[2] ibid. emphasis added.

previous

next