Group 18 elements - the noble gases

These elements, with the exception of helium, have the outer electronic configuration ns np . There is a stable octet of electrons in the outer shells of their atoms. Group 18 elements have the following properties in common  

The lighter members of the group do not combine with any substance, xenon reacts directly only with highly reactive fluorine  

Although they are all gases, the elements become more dense as the group is descended. 

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Table 15.9 The Group 18 Elements (the Noble Gases) Valence configuration ns2np6 Normal form colorless monatomic gas ...

TABLE 8.16 Properties of the Group 18 Elements The Noble Gases... 

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