This question comes from a second semester undergraduate organic chemistry course. Please refer to the image below with regard to the question.
My understanding of the trend in section 4a is that "larger" halogens such as iodine by themselves are able to stabilize positive and negative charges better than "smaller" halogens like fluorine.
Moving into section 4b, my professor transitions with "HOWEVER", telling me that the trend in 4b is contradictory in some way to the trend in 4a.
The idea that my professor is attempting to convey still very much eludes my comprehension. So I ask:
- (Main question) Why is iodine-containing molecule less stable than the fluorine-containing molecule?
- What is he trying to show me with this trend comparison?
- Is there a decent source that can elaborate on this section of my handout?