Which type of energy level is least stable in an atom?

• A. The lowest energy level (closest to the nucleus)
• B. The highest energy level (farthest from the nucleus)
• C. The middle energy level
• D. All energy levels are equally stable

Answer: (B)

Verified step by step guidance

1. Understand that in an atom, electrons occupy energy levels or shells, which are arranged at different distances from the nucleus.
2. Recall that the stability of an energy level is related to its energy: lower energy levels are more stable because electrons are held more tightly by the nucleus.
3. Recognize that the lowest energy level (closest to the nucleus) is the most stable because electrons there have the least energy and are less likely to be lost.
4. Know that the highest energy level (farthest from the nucleus) is the least stable because electrons there have higher energy and are more easily removed or excited.
5. Therefore, the least stable energy level in an atom is the highest energy level, which is farthest from the nucleus.