Answer:
FLUORINE
-Fluorine is a chemical element with the symbol F and atomic number 9. It is the lightest halogen and exists at standard conditions as a highly toxic, pale yellow diatomic gas. As the most electronegative element, it is extremely reactive, as it reacts with all other elements, except for argon, neon, and helium.
-Atomic number: 9
-Atomic mass: 18.998403 u
-Electron configuration: [He] 2s22p5
-Electronegativity: 3.98
-Van der Waals radius: 147 pm
-Discoverer: Henri Moissan
