The element that forms compounds with all other elements except helium, neon, and argon is fluorine (F). Fluorine is the most reactive nonmetal and has the highest electronegativity of all elements. This means that it has a strong tendency to attract electrons from other atoms, which allows it to form compounds with almost all other elements.

Helium, neon, and argon are all noble gases, which means that they have a complete outer electron shell and are very stable. This makes them very unreactive and unlikely to form compounds with other elements.