We have only to look around us
to recognize that our world is not a world of hydrogen and helium.
The chemistry in the first two chapters is quite inadequate for
dealing with our corner of the universe. For this, we need to understand
the heavier elements, which have more protons in their nuclei and
more electrons around them. As was mentioned in Chapter 2, the innermost
shell of any atom can hold a maximum of two electrons, and the second
shell can hold eight electrons.
We can build up a series of ten
atoms with increasing numbers of electrons, before we run out of
room in the first two electron shells. The next three chapters are
devoted to these simplest ten atoms. With them, we can outline the
chemistry of our world, although the heavier elements will be necessary
to fill in the details. These ten elements are the atoms of life,
for they make up 99.35 % of the material in any living organism.