A jester once remarked that two basic qualities distinguish humans from animals: their sense of humour and their sense of historical experience. A human being is capable of laughing over his own misfortune, and will not be caught a second time where he has stumbled once. We might add another quality, that of asking "why" and trying to find the answer.

   And now let us use this little word "why." 

   For instance, why are, the nonmetals not distributed evenly over the storeys and sections of the Big House, but grouped in definite part of it. Metals are metals and nonmetals are nonmetals, but what is the difference between them? Now that is a good question to start with.

   When two elements (no matter which) react, the outermost electron shells of their atoms are rearranged. The atoms of one of the elements gives away electrons, and those of the other accepts them. 

   Now the difference between metals and non­metals lies in this most important chemical law. 

   Nonmetals are capable of two opposite actions: as a rule, they acquire electrons. but they are also capable of giving them away. Their behaviour is pliable and they can change their aspect depending on the circumstances. If they find it more profitable to accept electrons, nonmetals appear as negative ions. If not, they form positive ions. Only fluorine and oxygen know no compromise: they only accept electrons and never give them away.

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