* Octet Rule: Atoms strive to achieve a stable electron configuration like the noble gases, which have a full outer shell (8 valence electrons).
* Reactivity: Elements with 7 valence electrons are only one electron away from achieving a full octet. This makes them highly reactive as they readily gain an electron to complete their outer shell.
* Example: Halogens (like chlorine, fluorine, bromine) are in Group 17 of the periodic table and have 7 valence electrons. They are highly reactive nonmetals.
* Stability: Elements with 8 valence electrons have a full outer shell and are very stable, meaning they are unreactive. This is why noble gases are inert.
In summary, elements with 7 valence electrons are highly reactive because they are one electron away from achieving a stable octet, while elements with 8 valence electrons are already stable and unreactive.
