Page 38 - Curriculum Visions Dynamic Book

The noble gases
The noble, or inert, gases are helium, neon, argon, krypton, xenon and radon. They make up a complete group (0) in the Periodic Table and the properties of
each member of the group are closely related to the others. The noble gases make up nine-tenths of 1% of the volume of the Earth’s atmosphere.
The noble gases are called inert gases because they do not usually react with any other element. Most elements react with one another because the combined atoms are more stable than the individual atoms. In fact, the most stable state generally occurs when the number of electrons in the outermost shell of an atom is eight. Reactions occur so that atoms can achieve eight electrons, either by losing electrons or gaining them from their partner. The noble gases are so stable, and react so little because, unusually for elements, the number of electrons in the outer part of the atom completely fill the shell. In all but helium the number of electrons in the outer shell is eight; for helium it is two
– the maximum possible in its only shell.
Not all of the noble gases are equally stable. For example, xenon can be made to combine with a few other elements, but helium combines with none.
Sir William Ramsay and the noble gases
Scientists can now tell what elements make up a substance by looking at the light it gives out when heated. The characteristic pattern of light is called a spectrum. Each element has a unique spectrum that can be readily picked out by an instrument called a spectrometer.
In the middle of the last century when scientists looked at the wavelengths of light being given out by the Sun, they could identify all of them except for a mysterious yellow light. This was helium. Helium was discovered on Earth in
a sample of rock in 1895 by a Scotsman, William Ramsay, who then went on to discover all the other noble gases.
Helium
 Sir William Ramsay experimenting with radium in his laboratory.
Neon
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