text: This element is commonly stored in nickel containers as it forms a passivation layer.
full_question: This element is commonly stored in nickel containers as it forms a passivation layer. Because the Sandmeyer reaction does not effectively add this element to aryl compounds, the Balz-Schiemann reaction is used instead. Carboxylic acids substituted with this element are much more acidic due to this element's strong inductive effects. The first noble gas compound discovered consisted of an atom of xenon bound to four atoms of this element. This element and hydrogen form an acid which etches glass and can diffuse through skin down to the bone. For 10 points, name this most electronegative element that has an atomic number of 9 and is the lightest halogen.
first_sentence: This element is commonly stored in nickel containers as it forms a passivation layer.
raw_answer: fluorine [prompt on F]