HESI A2 SCIENCE Practice Test

Xenon is considered a noble gas because it belongs to Group 18 of the periodic table, which is known for having elements that are chemically inert or non-reactive under standard conditions. Noble gases have a full valence shell of electrons, which makes them stable and unlikely to form bonds with other elements. This characteristic contributes to their low reactivity compared to other elements.

Oxygen, hydrogen, and nitrogen are all non-metals that do not have a full valence shell, making them more reactive and capable of forming various compounds. Oxygen, for example, readily combines with many other elements to form oxides, while hydrogen can form bonds with a wide range of non-metals and metals. Nitrogen, too, is known for its reactivity, especially in the formation of ammonia and other compounds. Thus, xenon's status as a noble gas sets it apart from these other elements due to its lack of reactivity and full outer electron shell.