It was in January 1955 that the Atomium project, which I presented to the Belgian Metal Industries, entered the design phase in order to be erected at the 1958 exhibition.

The Atomium is a symbol of the atom concept, because it represents a crystal mollecule (sic) of metal, actually of the centered cubic system.

In this crystal system, the atoms are replaced on the vertexes of a cube, and one atom occupies its center.

The elementary centered cubic system is composed of 9 atoms places as shown in Fig. 1. (picture of A. Waterkeyn and model of Atomium)

In crystal chemistry, the structure of crystals is commonly represented by spheres the centers of which materialise the mean position of the atom in the crystal network; the binding forces which exist between the atoms are materialised by links interconnecting the spheres. These binding forces are the essential cause of the chemical properties and the mechanical resistance of the different elements, and particularly metals; it is thus perfectly logical to clearly mark their existence in any representation of crystals.

Starting from the basic idea of a crystal of metal at atomic scale as a symbol - which was suitable for both the metal industry, promoter of the project, and the Exhibition, I thought of considerably increasing (in fact, 165 billion times) the distances which separate the centers of the atom in the cristalline (sic) system, so as turn them into a construction in which the spheres representing the atoms would be of sufficient size to house the exhibits relative to this branch of science.

The public had to be able to move from one sphere to the other without effort, which meant placing escalators in the inclined tubes representing the binding forces; this condition led to choice of diameter for the interconnecting tubes. The dimensions which I initially proposed for the actural spheres (a diameter of about 65.6 ft) were not directly scaled up from the actual steel atom dimensions because, if this had been the case, they would have been larger. The diameter finally chosen (59 ft) was a compromise between a hall of suitable size and practicability of construction.

The particular position chosen for the cube, i. e. resting on one sphere with a vertical diagonal, was essentially dictated by esthetical reasons. Such a position made it of course necessary to insure the stability of the structure by three pylons called "bipods"; the have two principal functions:

a) Support the three lower spheres of the Atomium;
b) Allow the installation of the stairs, which are essential to evacuate the public entering the Atomium by the base sphere.

The basic structure of the construction had to be of steel and the skin of the 9 spheres in aluminium. The spheres that could be visited had to have at least two floors, the levels of which had to coincide whth the linking tubes penetration points.