ABSTRACT
The rare gases, sometimes referred to as noble gases, are situated in the zero group in the
periodic table of elements between the most electronegative (the halogens) and the most
electropositive (the alkali metals) elements. Because their electron shells are completely filled,
they are inert, that is, do not normally form chemical compounds. Their ionization energy,
the energy required to remove an electron from the valence shell, is greater than for any other
element, and conversely, their electron affinity, the energy released in taking up another
electron, is zero. Nevertheless, it has been found that for the heavier inert gases, whose
outer electrons are farther removed from the nucleus and whose force of retention is weaker,
and electrons can indeed sometimes be removed by strong electromagnetic fields. Fluorides of
krypton, xenon, and radon have thus been prepared, and recently krypton has actually been
inserted into acetylene mainly to form an ionic bond with carbon. (One may thus say that a
more appropriate classification in the periodic table would be in group VIIIA.) (Table 4.1).
