MAGNESIUM CHLORIDE MgCl,

Magnesium is a tetrahedron. It has no centre but has four rather wide funnels, each containing three segments.

Chlorine has a dumb-bell shape. The centre of a Chlorine atom is the group of five Anu in the central bar or rod. This body of five Anu is described as hard and positive. Positive bodies are hard, and negative softer and more spongy. When the Chlorine breaks up each body of five Anu takes one end of a Chlorine atom with it and floats over a negative funnel of Magnesium. The remaining four bodies from the central rod, two of four Anu and two of three Anu, go with the second end of a Chlorine atom and float over a positive funnel. These four bodies revolve round a common centre of gravity, not in a perfectly flat surface. The 12 funnels at the ends of the Chlorine atoms arrange themselves in a flower shape round their own central globe. As has been said, only three funnels can be shown. Two Magnesium funnels have the flower and a group of four bodies, while two Magnesium funnels have the flower and the group of five Anu. One of these latter groups is not shown. Thus all the constituents of the Magnesium and the Chlorine atoms are accounted for.

FERRIC CHLORIDE FeCl,

FERRIC CHLORIDE FeCl,

There are to be accounted for in Iron, fourteen bars radiating from a cube, as in the diagram of the Bars group, then three Chlorine atoms giving three rods, three C1.19 groups forming the centre of the dumb-bell of Chlorine and six flowers, each with a centre NalO and 12 funnels, making 72 funnels in all.

In the molecule FeCl,. the three rods of Chlorine make three spheres and place themselves at the centre of the cube. Round these, but still inside the bars of Iron, rotate the six NalO balls, each at the corner of an octahedron. These make a grand centre inside the Iron atom. The bars of Iron stick out from the cube on to the surface of a sphere. Fig. 177.

In the diagram it is not possible to show all the funnels, so 36 only are shown. They are in groups of three and are intended to be thought of as sticking out like spikes.

ANTIMONY BROMIDE SbBr3

ANTIMONY TRIBROMIDE SbBr,

Antimony is a cube. It has six funnels and no centre.

Bromine is a dumb-bell with its rod or bar like that of Chlorine, C1.19, and having a globe and twelve funnels at each end.

In Antimony Bromide the Antimony is not much changed save that parts of the Bromine atoms enter into the centre of the cube and form a grand centre. Fig. 178.

The Bromine atoms break up. Over each Antimony funnel there floats one flower of 12 funnels and a globe. The six funnels and flowers point to the faces of a cube. In the diagram the cube is indicated but only four of the six funnels and flowers are drawn.

The three rods break up and rearrange themselves as a grand centre within the cube of the Antimony. Each rod consists of a group of five Anu. two groups of four Anu and two groups of three Anu.

In the very centre there come the three groups of five Anu, one from each of the rods. These five Anu are themselves at the corners of a tetrahedron (a five-sided figure, not a regular tetrahedron but a pyramid.) These three groups of five Anu arrange themselves in a special formation. One stands at the top and another at the bottom of a vertical line. The third runs round in a ring, like the edge of a disc, which cuts horizontally the vertical line drawn between the other two. The ends of the vertical line move but comparatively slowly, while the middle group of five Anu moves very fast. The whole arrangement then goes head over heels, having a curious double motion.

Round this central group the other bodies, six groups of four Anu and six groups of three Anu, are arranged as follows:

Take a cube and place inside it, at the centre, the set of three fives as already described. Then take the central points of the sides or faces of the cube and at each of these is a body of four Anu. This gives the position of the six fours. Then take a second cube and set it a little cornerwise cutting the first cube ; then take the middle points of the faces of this cube. At the middle points are the six bodies of three Anu. It will be seen that these middle points of the faces of a cube are really at the points of an octahedron ; if we place the groups of one four and one three fairly near together and at the corners of an octahedron we get the idea of the arrangement. The diagram attempts to indicate this. The whole of these threes and fours are said to be in placed in a sphere which forms the grand centre of the Antimony Bromide molecule. This has been indicated in the diagram.

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