Answer:
They're never found as individual elements in nature because they are so reactive.
Step-by-step explanation:
Halogens are a highly reactive group of elements. They are usually found combined in nature. 
- Because each of the elements has seven electrons in the outer shells of their atoms the elements are all univalent and also acceptors of electrons. 
- They are all non-metals and oxidizing agents. 
- This makes the elements in this group highly reactive and combine readily with other species in nature.