Which of the following alkali metal does not form alum ?

When heated in excess of air, alkali metals form different types of oxides depending upon the nature of the metal. Which of the following alkali metals form surperoxides ?

Which of the following alkali metals form complex hydrides?

Which of the following alkali metals form complex hydrides?

Alkali metals react with water vigorously to form hydroxides and dihydrogen. Which of the following alkali metals reacts with water least vigorously

Alkali metals react with water vigorously to form hydroxides and dihydrogen. Which of the following alkali metals reacts with water least vigorously ?