The element astatine (At), which appears at the bottom of the halogen column in the periodic table, has been prepared artificially in minute amounts but has not been found in nature. Using the periodic law and your knowledge of the halogens, predict the properties of this element, as follows:
a. At room temperature, is it solid, liquid, or gaseous?
b. How many atoms does a molecule of its vapor contain?
c. Is it very soluble, moderately soluble, or slightly soluble in water?
d. What is the formula for its compound with hydrogen?
e. What are the formulas for its compounds with potassium and calcium?
f. Is its compound with potassium more or less stable than potassium iodide?