Changes

: An [[atom]] of [[Fluorine]] has only 2 [[electron]]s in its [[Outer Shell|outer shell]].

: [[Fluorine]] [[ion]]s gain 1 [[electron]] to get a full [[Outer Shell|outer shell]] and become [[Negative Charged|negatively charged]].

#Collect the [[gas]] in a [[Test Tube|test tube]].

#Place a piece of [[Litmus Paper|litmus paper]] over the mouth of the [[Test Tube|test tube]].

#If the [[Litmus Paper|litmus paper]] is [[bleach]]ed white then the [[gas]] is [[Fluorine]] or [[Chlorine]].