A Fluorine B Nitrogen C Arsenic D Aluminum
A FluorineNot sure what level you're at, but I'm doing Chemistry Revision anyway so it would do me good to try and explain itBasically, Flourine has 7 electrons in it's outer shellAll atoms want to become stable and inert (unreactive) like the noble gases, neon, argon etcSo, as Flourine atoms only require one more electron to have a full outer shell on electrons, and it's outer shell is closest to it's nucleus, it is most reactiveBromine and Iodine atoms are much less reactive, as their outer shells are further from their nucleus, meaning that the force pulling the extra electron to it is much less strongHope that helps ;) Note To Daniel - Flourine is in the top right, it's Francium which is bottom left, but that is the element which will most readily LOSE an electron :/
