The chemistry of francium is not known.
Francium is not a compound, but a chemical element.
Its an element.
Francium chloride is a radioactive chemical compound with the formula FrCl. It is predicted to be a white solid and is soluble in water. Its properties resemble caesium chloride. It is produced by the reaction of hydrochloric acid with francium metal. Source: Wikipedia
If by vital you mean most reactive, then the metal francium, Fr, is the most reactive element.
Francium sulfide is the compound that contains francium and sulfur.
The element is francium.
Hydrogen and francium can combine to form a compound with the formula HFr, which stands for hydrogen francium. This compound would be highly unstable and reactive due to the extremely high reactivity of francium. Francium is a rare and radioactive element that is highly unstable and difficult to handle, making it unlikely to form stable compounds with hydrogen.
Francium is the chemical element with the atomic number 87.
'FrCl' is Francium chloride. NB Francium(Fr) is the heaviest of the Group(I) [Alkali] metals. You will not find it in the open lab. because it is radioactive.
When francium and oxygen react, francium oxide is formed. This compound is highly reactive and unstable due to francium's extreme reactivity. Francium is a highly radioactive element and is extremely rare in nature.
Francium has not applications and the oxide cannot be prepared.
The compound formed between sodium and francium would be NaFr, with sodium as the cation and francium as the anion. This compound would have a 1:1 ratio of sodium to francium ions.