Respuesta :
The correct answer is the outermost electron shell.
The outermost electron shell, or valence electron shell, is involved in chemical bonding with other atoms. It is for this reason that groups on the periodic table (columns of elements like the nobles gases) have similar properties; their similar chemical properties arise from the fact that they have the same number of valence electrons. Valence electrons are involved in bonding because each atom looks to have a complete valence shell. For some elements, this is most easily obtained by losing electrons (making a cation, or positive ion). For other elements, this is most easily obtained by gaining electrons (making an anion, or a negative ion).
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