Answer: They all have the same valance electrons i.e. 7 valence electrons
Explanation: The elements in-group 7 are often referred as “halogens”. When they form ions, they tend to gain an electron and form negative ions. They are all non-metals and their reactivity down the group decreases because the atomic radius increases in size with an increase of electronic energy level (so fluorine is the most reactive halogen of group 7)
