The Periodic Law with Halogens
Take a look at the halogens on the periodic table, the non-metallic elements found in group 17. The elements in this group contain fluorine (F), chlorine (Cl), bromine (Br), iodine (I), and astatine (At). Remember periodic law? It states that “when elements are arranged in order of increasing atomic number, there is a periodic repetition of their chemical and physical properties.” In the case of these halogens, they are all act very similarly with each other in chemical reactions and are extremely reactive (because they only need 1 valence electron to complete the shell).
Take a look at this video starting at 1:15
Why are they using iron wool to test these elements?
Does the reactivity increase or decrease when going down the group?
If the scientists in the video decided to test fluorine, what do you think would happen?