Fluorine (named from fluo or flow is the ninth element.  It has an atomic number of nine and an atomic mass of 19.  There are two electrons in the 1s orbital, two electrons in the 2s orbital, two electrons in the 2p_x orbital, two electrons in the 2p_y orbital and a single electron in the 2p_z orbital.  Fluorine easily gains one electron to become an anion having a negative charge.  The molecule, F₂ is so reactive that it will corrode platinum, a metal that resists most other chemical compounds.