Fluorine

 The chemical element F is Fluorine. 🦷

Here is some essential information about it:

 * Symbol: F

 * Atomic Number: 9

 * Atomic Mass: \approx 18.998 u

 * Classification: Halogen (Group 17), and the lightest member of this group.

 * State at Standard Temperature and Pressure (STP): Pale yellow, highly toxic, diatomic gas (\text{F}_2).

Fluorine is the most electronegative and most chemically reactive of all elements. Due to this extreme reactivity, it is never found in its pure form in nature. Its compounds are widely used:

 * Dental Health: The fluoride ion (\text{F}^-) is added to toothpaste and drinking water to help prevent tooth decay by strengthening tooth enamel.

 * Non-stick Materials: It is a key component in Teflon (Polytetrafluoroethylene or PTFE), known for its non-stick properties.

 * Nuclear Energy: It is used in the production of uranium hexafluoride (\text{UF}_6), which is critical for uranium enrichment in the nuclear fuel cycle.

You can learn more facts about this highly reactive element from this video: Fluorine Chemical Element - Periodic Table | Properties & Uses!.