Why are the noble gases the least reactive elements?
The noble gases are the least reactive elements because they have a complete outer electron shell. A complete outer shell means that the noble gases have achieved a stable electron configuration, resembling the noble gas configuration, known as the octet rule.
The octet rule states that atoms tend to gain, lose, or share electrons in order to achieve a stable electron configuration with eight electrons in their outermost energy level (except for helium, which has two electrons in total). This stable configuration provides greater stability and lower potential energy for the atom.
Noble gases already have the desired number of electrons in their highest energy level, making them very stable and unreactive. Since they have no need to gain, lose, or share electrons to achieve stability, they do not readily form compounds with other elements or engage in chemical reactions. This is why they are considered inert or non-reactive.