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crystal of common salt (sodium chloride). It is composed of atoms of sodium and chlorine. When it is dissolved into water it dissociates into positive (snigdha) ions of sodium and negative (rüksa) ions of chlorine. The equation is
NaCl = Na +CI' or in the case of Copper Sulphate (Nila Tutiya)
CuSO4=Cu +S04" (Dots are used at the top to denote snigdha atoms and dashes to denote ruksa.)
Referring again to gathā 615 of the Gommat asāra quoted on page 155 ante we see that the necessary condition for union is that the combining particles or atoms should differ in energy level by two units. These units it is difficult to identify but it appears to be a sort of Exclusion Principle, and might, if properly interpreted, to be used to explain the periodicity of the systems of the electrons in atoms, as does the Pauli's Exclusion Principle. There is no doubt, however, that there are various kinds of union differing in degrees of strength. "A question", said Sir Venkata Raman once, “of fundamental importance both to the physicist and to the chemist is, why do atoms combine to form molecules?" The learned professor then continues to say “we are not yet in a position to give a complete answer to this question. The facts of chemistry, however, compel us to recognize that chemical combination may be of different kinds. As an example of one type of chemical combination, we may instance the case of common salt. The elements sodium and chlorine when allowed to come in contact combine with explosive voilence to form salt. Nevertheless when we dissolve common salt in water, there are excellent grounds for believing that the substance breaks up again into electrically charged atoms of sodium and chlorine respectively, We have quite a different type of combination when two atoms of the same element as, for example, oxygen, combine to form a molecule of the element." When oxygen, dissolves in water the molecule does not dissociate again into separate atoms.336
335. Sodium atoms combining with chlorine atoms is a case of snigdha uniting with ruksa, whereas two oxygen atoms combining to form a molecule of oxygen is a case of ruksa uniting with ruksa.
336. It shows that in this case the bond between oxygen atoms is much stronger than that between sodium and chlorine atoms in a molecule of common salt.
