Fluoride is moderately basic, by far the most basic of the halides. It is a terrible leaving group. Fluoride is many orders of magnitude better than bromide in leaving group ability. Bromide is many orders of magnitude better than fluoride in leaving group ability. Bromide ion is so weak it is not considered at all basic; it is an excellent leaving group.

  Bromide is many orders of magnitude better than fluoride in leaving group ability

Explanation:

As Size of an atom  Increases,  the Basicity Decreases this is because  if we move downwards  from the top of the periodic table to the bottom of the periodic table, the size of an atom increases. As size increases, basicity will decrease, meaning the element  will be less likely to act as a base implying that the element will be less likely to share its electrons.

in the same vein. With an increase in size, basicity decreases, making the ability of the leaving group to leave increase to increase . This can be seen in the halogens going down the group  from

F--- worst

Clfair

Br good

 Iexcellent

with fluorine having the worst ability to leave than Bromine which is better in terms of the leaving group ability.

i just calculated it all out, and not including weekends, and all the different days off. as of this school year (2018-2019) students are spending 2198 hours in school this year