II AND IIa.—THE TETRAHEDRAL GROUPS.
II.—This group consists of beryllium (glucinum), calcium, strontium and barium, all diatomic, paramagnetic and positive. The corresponding group consists of oxygen, chromium, molybdenum, wolfram (tungsten) and uranium, with a blank disk between wolfram and uranium: these are diatomic, paramagnetic, and negative. We have not examined barium, wolfram, or uranium.
[Illustration: PLATE VIII.]
BERYLLIUM (Plate III, 2, and Plate VIII, 1). In the tetrahedron four funnels are found, the mouth of each funnel opening on one of its faces. The funnels radiate from a central globe, and each funnel contains four ovoids each with ten atoms within it arranged in three spheres. In the accompanying diagrams one funnel with its four ovoids is shown and a single ovoid with its three spheres, containing severally three, four, and three atoms, is seen at the left-hand corner of the plate (7 a). The members of this group are alike in arrangement, differing only in the increased complexity of the bodies contained in the funnels. Beryllium, it will be observed, is very simple, whereas calcium and strontium are complicated.
BERYLLIUM: 4 funnels of 40 atoms 160
Central globe 4
Atomic weight 9.01
Number weight 164/18 9.11
CALCIUM (Plate VIII, 2) shows in each funnel three contained spheres, of
which the central one has within it seven ovoids identical with those of
beryllium, and the spheres above and below it contain each five ovoids (7
b) in which the three contained spheres have, respectively, two, five,
and two atoms. The central globe is double, globe within globe, and is
divided into eight segments, radiating from the centre like an orange; the
internal part of the segment belonging to the inner globe has a triangular
body within it, containing four atoms (7 c), and the external part,
belonging to the encircling globe, shows the familiar “cigar” (7 d). In
this way 720 atoms are packed into the simple beryllium type.
CALCIUM: 4 funnels of 160 atoms 640
Central globe 80