Noble gas An element in Group

Noble gas An element in group 18 at the far right of the periodic table, 31 anions, 38 cations, 38 characterization, 190 structures, 150-151... 

Noble gas An element in Group 18 (VIIIA) of the periodic table. 

The elements in the column to the far left on the periodic table are called group lA elements or alkali metals. They all have one valence electron and are very reactive. In their reactions, they lose that valence electron to acquire an electron configuration like that of a noble gas. The elements in the second column of the periodic table are called group 2A elements or alkaline earth metals. They have two valence electrons and lose them in chemical reactions to acquire a noble gas electron configuration. 

Typical elements in Groups V. VI and VII would be expected to achieve a noble gas configuration more easily by gaining electrons rather than losing them. Electron affinity is a measure of the energy change when an atom accepts an extra electron. It is difficult to measure directly and this has only been achieved in a few cases more often it is obtained from enthalpy cycle calculations (p. 74). 

What is true for sodium is also true for the other elements in group 1A All form positive ions by losing their valence-shell s electron, and all the resultant ions have noble gas electron configurations. Similarly for the elements in group 2A All form a doubly positive ion by losing both their valence-shell s electrons. An Mg atom (Is2 2s2 2p6 3s2), for example, goes to an Mg2+ ion with the neon configuration Is2 2s2 2p6 by loss of its two 3s electrons. 

Helium is a member of the noble gas family. The noble gases are the elements in Group 18 (VIIIA) of the periodic table. The periodic table is a chart that shows how the elements are related to one another. The noble gases are also called the inert gases. Inert means that an element is not very active. It will not combine with other elements or compounds. In fact, no compounds of helium have ever been made. 

We know through observation that eight electrons (an electron octet) in an atom s outermost shell, or valence shell, impart special stability to the noble-gas elements in group 8Aof the periodic table Ne (2 + 8) Ar (2 8 -f S) Kr (2 -f... 

The elements in groups 1, 2 and 13 have only 1, 2 or 3 electrons in their outer shell. These elements at the beginning of a period lose electrons to form positive ions (cations). The resulting simple ions obey the octet rule (eight electrons in the outer shell) and have an electron arrangement like the noble gas at the end of the previous period. 

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