3 Chemistry can often be explained by electronic structure
Section 2 used some simple examples to illustrate chemical periodicity. But how can we explain such periodicity? The answer lies in the way that the electrons in atoms are arranged about the positively charged nucleus. In chemical reactions, atoms change partners. We know that the outsides of atoms consist of electrons, so contact and connection between atoms is likely to take place through their electrons, and in particular, through the electrons in their outer shells. So similarities in the arrangement of the outer electrons in the atoms of two different elements lead to similarities in the chemistry of the two elements. To see the truth of this idea, you must be able to write down the electronic configurations of atoms.