Which of the following best explains why elements in Group 18 (noble gases) are generally non-reactive?

• A. They have a complete valence electron shell, making them chemically stable.
• B. They have the highest metallic character in the periodic table.
• C. They easily lose electrons to form positive ions.
• D. They have the smallest atomic radii, preventing reactions.

Answer: (A)

Verified step by step guidance

1. Understand that chemical reactivity is largely determined by the electron configuration of an element, especially the electrons in the outermost shell (valence electrons).
2. Recall that Group 18 elements, known as noble gases, have a full valence shell of electrons, which means their outermost energy level is completely filled.
3. Recognize that a complete valence shell leads to chemical stability because these atoms have little tendency to gain, lose, or share electrons, which are the processes involved in chemical reactions.
4. Compare this to other groups where atoms tend to react to achieve a full valence shell by losing, gaining, or sharing electrons, making them more reactive.
5. Conclude that the best explanation for the low reactivity of noble gases is their complete valence electron shell, which makes them chemically stable and unlikely to participate in reactions.