PRESIDENTIAL ADDRESS SECTION B. 59 



it. In the case of such a compound as chlorobenzene, however, 

 the chlorine is completely un-ionised and it is to be assumed that 

 the chlorine is much closer to the rest of the molecule and has an 

 electron in common with the carbon to which it is attached. The 

 chlorine "shell" is a cube* and the carbon "shell" a tetrahedron, 

 and the corner or point of junction is the same electron. Generally 

 speaking, the conception is that when 8 electrons get established 

 round a nucleus the result is a saturated body which is incapable 

 of further chemical action : it is only rendered active again by 

 electrolysis or analogous process. 



There are great difficulties in accepting Gilbert Lewis's octet 

 theory of valence for the lower elements, although it is probably 

 true for the higher elements. The new suggestion I wish to bring 

 forward is, as already said, that the arrangement or structure of 

 the nucleus governs the structure of the valency electrons in the 

 smaller atoms. The nucleus, although its actual weight has nothing 

 to do with chemical properties, thus indirectly influences the 

 direction in space of the valency electrons and consequently affects 

 the chemical properties of the atom by its arrangement, not by its 

 size. Thus to make my position quite clear even at the risk of 

 repetition, the arrangement of the carbon nucleus has the shape 

 of a regular tetrahedron, that of the nitrogen-nucleus, the shape of 

 a tetrahedron or pyramid with one point farther from the c?ntre 

 than the other three, and that of oxygen the shape of an irregular 

 tetrahedron with two points nearer and two points farther from 

 the centre. Each valency electron in the case of carbon has its 

 average position iu line with a projection of the nucleus, giving 

 a regular tetrahedral result. 



In nitrogen, 3 of the valency-electrons are arranged as in 

 carbon, namely in line (from the centre of the nucleus) with the 3 

 nuclear points which are nearer the centre: whilst the other two 

 form a saturated pair lying opposite the fourth point of the nucleus 

 where the group X+ is attached to the nucleus. Putting Z++ for 

 H+ H+ 



and X+ for H+ 6 H+, the carbon nucleus becomes 

 H+ 

 (Z,++ + 26) (see Fig. 7), the carbon kernel becomes (Z,++ + 2(9)2(9, 

 and the carbon atom becomes r(Z, ++ + 20) 26 + 40] the 



whole arrangement being tetrahedral. The nitrogen nucleus 

 is (Z. + + + 26 + X+) or (Z,++ + 26 + Z++X+) the nitro- 

 gen kernel has two more electrons, so»that the nitrogen atom is: 

 6 



Or Sir J. J. Thomson's skew-eubo ("i-.ku.be"). 

 7 



