In this task you will be given a text passage from a trivia quiz. You should choose the category this question belongs to from these categories: History, Science, Social Science, Fine Arts, Literature. You can only choose one category, so if in doubt, please choose the closest match.

The presence of this element at the center of sarin allows it to inhibit acetylcholinesterase. This element bonds to an azide in the first step of the Staudinger reduction. A functional group containing this element in its center stabilizes the carbanion in the intermediate of the Horner-Wadsworth-Emmons reaction. Four atoms of this element bind to 10 oxygen atoms in its (*) pentoxide. A Z-alkene can be produced by reacting a carbonyl with an ylide with positive charge on this element in the Wittig reaction. Coming in notable white and red allotropes, for 10 points, name this element with atomic number 15 which is found below nitrogen on the periodic table.
Science