How do atoms attain nobel gas …

Elements forming covalent compounds achieve noble gas configuration by sharing electrons within the atoms, unlike ionic compounds which achieve the noble gas configuration either by gaining or losing electrons from the outermost electron shell.  Atoms attain noble gas configuration by gaining or losing electrons in order to satisfy the role of an octet.
 

Atoms want a full outer shell because it completes all the gaps in the outside. With no gaps, other electrons don't want to fit into those spaces. For example, a noble gas like Neon has a full outer shell. It doesn't react with other chemicals because the electrons from other chemicals can't fall in anywhere. Elements forming covalent compounds achieve noble gas configuration by sharing electrons within the atoms, unlike ionic compounds which achieve the noble gas configuration either by gaining or losing electrons from the outermost electron shell.