HESI A2 Chemistry Practice Test

Noble gases are characterized by their very low reactivity, which is due to their full valence electron shells. In the periodic table, noble gases occupy Group 18 and include helium, neon, argon, krypton, xenon, and radon. These elements have eight electrons in their outermost shell (with the exception of helium, which has two), creating a stable electron configuration that does not tend to gain or lose electrons. This stability means that they do not typically form chemical bonds with other elements, making them mostly inert under standard conditions. The lack of reactivity is what allows noble gases to exist in nature as monatomic gases. They do not readily participate in reactions due to their complete valence electron shells, which contrasts sharply with other groups in the periodic table that are more reactive, such as alkali metals or halogens. Therefore, the characteristic of very low reactivity is a defining feature of noble gases and helps explain their unique behavior in chemical reactions.