As valence shell is defined as the outermost with electron occupied tray in the electron shell of an atom . It contains the valence electrons that are available for entering into chemical bonds (" valences "). The configuration of the valence shell largely determines the chemical properties of the atoms of a chemical element .
The valence shell can hold a maximum of eight electrons for elements of the main groups , namely 2 in the s orbital and 6 in the p orbitals. An exception are the elements hydrogen and helium , in which only the first shell (1s) is occupied - in the case of helium, it is already fully occupied with 2 electrons.
All noble gases except helium have 8 electrons in the valence shell ( noble gas configuration ). According to the octet rule , chemical compounds are usually in a "stable state" when all atoms involved reach the noble gas configuration by accepting or releasing electrons to their binding partners ( ionic bond ) or by forming common electron pairs ( molecular bond ) .