Answer: I think that you have to find it in your lesson
Explanation:
The element which is least likely to undergo a chemical reaction is (4) neon.
The reason for this is because neon is a noble gas, which means that it doesn't react with other elements as well.
Answer:
if you mix any halogen with any alkali then ionic salt will be formed and also this will cause an exothermic reaction in which heat is getting released