[grey_whiskers]

Which two elements are you comparing?
Freepmail.

[TheConservativeParty]

6 Year Delta

https://pbs.twimg.com/media/GHzfAnqacAAkoue?format=jpg&name=900x900

[goldbux]

Reactivity slide . . .
–––––

CDY is comparing fluorine [F] with chlorine [Cl].

These two elements are members of the halogen group of the periodic table, along with bromine [Br], iodine [I] & astatine [At].

Fluorine is one of the most reactive and dangerous elements.
Halogen-group elements easily bind with other substances.