The Greek notion of atoms and elements survived for many centuries, and it was eventually fleshed out with a few more elements, mostly through the efforts of the alchemists. Some elements such as gold were discovered much earlier. By the late eighteenth century, the idea of an element as a substance that cannot be broken down into more fundamental substances was beginning to be accepted. In 1789 Antoine Lavoisier (1743 – 1794) produced a list of 33 elements; missing from this list were earth, air, fire, and water; but it did contain light and heat – along with a number of modern elements, including cobalt, mercury, zinc, and copper. That oxygen and hydrogen were elements, while water was not, had been established. The stage was set for a rapid growth in our knowledge about the underlying structure of matter.

1.1 Atoms
1.2 Realities
1.3 History
1.4 Elements
1.5 Evidence
1.6 Parts
1.7 Iinteractions
1.8 He and H₂

We now know of 91 naturally occurring elements, and quite a number of unnatural, that is man-made ones. As we will see, these man-made elements are heavier in atomic terms than the naturally occurring elements and are typically generated by smashing atoms of natural elements into one another; typically they are unstable and rapidly "decay" into atoms of other elements.

As examples of how science can remove some of the mystery from the universe: our understanding of atoms and elements means that no new “light” elements are theoretically possible, we know all the light elements that can possibly exist anywhere in the universe (a pretty amazing fact). Similarly, our current understanding of the theory of general relativity and the laws of thermodynamics make faster than light travel and perpetual motion machines impossible (although it doesn’t stop people from speculating about them).

The first modern chemical isolation of an element is attributed to the alchemist Hennig Brand (c. 1630 – c. 1710)[link]; he isolated phosphorus from urine while in pursuit of the Philosopher’s stone. While this may seem like an odd thing to do, people have done much stranger things in pursuit of gold or cures for diseases like syphilis. Imagine his surprise when, after boiling off all the water from the urine, the residue burst into flames and gave off a gas that, when condensed, produced a solid that glowed green in the dark. It was for this reason that he named it phosphorus, from the Greek for "light-bearer." Similarly, mercury was originally isolated by roasting the mineral cinnabar; while mercury is quite toxic, it was used as a treatment of syphilis prior to the discovery of effective antibiotics.

Question to answer:

• How would you explain the difference between an atom and an element?
• What differentiates one element from another?
• What is the difference between an atom and a molecule?
• What is the difference between an element and a compound?
  

Questions for ponder:

• What types of evidence might be used to conclude that you had isolated a new element?
• What types of elements would be difficult to identify?
• When can unproven/unsubstantiated assumptions be scientific?
• Under what conditions are such assumptions useful?