ABSTRACT
The ancient Greeks – and especially Democritus – had the idea of a single elementary particle, but their science did not extend to observation and experiment. For that, we as human had to wait nearly 22 centuries until Dalton, Avogadro and Cannizzaro formulated atomic theory as we know it today. This chapter deals with the concepts of energy as applied to changes of state, from gases to liquid, briefly, and from liquid to solid, more extensively, including consideration of equilibrium and equilibrium diagrams. An extremely important factor governing the properties of an element is the number of electrons in the outermost shell since it is these that are most readily available to form bonds with other atoms. An obvious limitation of the ionic bond is that it can occur only between atoms of different elements, and therefore it cannot be responsible for the bonding of any of the solid elements.
