revision pg. 124

The noble gasses The chemists s’interessent themselves to the noble gasses because of their weak reactivity. Many laboratory experiences showed that all the noble gasses chemically are "stable". These gasses do not possess any non matched electron. Each of the colors of an advertising sign originates of a different noble gas. The halogen The halogen ones exist to the natural state in the form of a composites, because the atoms of the halogen one react vigorous with almost other any element. In fact, asthe atoms of the alkaline metals, the atoms of the halogen ones possess a non matched électron. But they one plutot the tendency has acquerir an electron to form composites.