Schema molecular structure

This creates a table of four columns in the schema achemcompany. The column named smiles is intended to store the SMILES representation of a chemical structure, the id column will store an integer identifier to be used for joining other tables, the column mw will store the molecular weight with a precision of 2 digits to the right of the decimal point, and the column named added will record when this structure was entered into the table. As defined above, any character string could be entered into the smiles column, any integer into the id column, and any valid... 

Just as the atom takes on a significance in learning about chemistry which is not justified in terms of the (lack of) role that discrete atoms play in chemical processes, once learners have been taught about molecules there is a tendency to apply the molecule schema to all structures. The role of valency in limiting, if not exactly determining, molecular formulae, may be extended to metals and to ionic materials. Metals may be seen by students to consist of discrete molecules of similar atoms, in a similar way to iodine or phosphoms. In the ionic case, valency is seen by many students to indicate the number of ionic bonds that can be formed, and not just the charge on the ions. 

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