Question

which of these elements is the least reactive?
a. sodium
b. krypton
c. chlorine
d. aluminum

Explanation:

Krypton is a noble gas with a full - valence electron shell, making it very stable and least reactive among the options. Sodium is a metal in Group 1, chlorine is a halogen, and aluminum is a metal in Group 13, all more reactive than krypton.

Answer:

B. krypton