High Quality Content by WIKIPEDIA articles! Caesium fluoride (cesium fluoride in North America), is an inorganic compound usually encountered as a hygroscopic white solid. It is more soluble and more readily dissociated than sodium fluoride or potassium fluoride. It is available in anhydrous form, and if water has been absorbed it is easy to dry by heating at 100 °C for two hours in vacuo. Like all soluble fluorides, it is mildly basic. A notable fact about this compound is that it is the most ionic compound. Caesium has the lowest electronegativity and fluorine has the highest electronegativity.