Question

The oxidation number of oxygen is almost always 2- in a compound. Exceptions to this rule would be peroxides, O2^(2-) where the oxidation number of each oxygen is 1-, and superperoxides, O2^(-1) where the oxidation number of each oxygen is 1/2-. Neither peroxides nor superperoxides are common. Peroxides are only known to form compounds with the elements in the first two columns of the periodic table.

Which elements are known to form superperoxides?

A) Hydrogen, lithium, and sodium
B) Potassium, rubidium, and cesium
C) Boron, aluminum, and gallium
D) Carbon, silicon, and germanium

Answer 1

The elements known to form superoxides, compounds in which oxygen has an oxidation number of –1/2, are potassium, rubidium, and cesium (Option B).

Step-by-step explanation:

The oxidation number of oxygen in most compounds is typically -2, but in peroxides and superoxides, it differs. Peroxides and superoxides are compounds where oxygen has oxidation numbers of -1 and -1/2, respectively. Peroxides are known to form with elements in the first two columns of the periodic table, while superoxides form with elements that are heavier alkali metals.

The elements known to form superoxides, which have oxygen with an oxidation number of -1/2 in the compound, are potassium, rubidium, and cesium. These elements are all in the first column of the periodic table but are heavier than lithium and sodium, which typically form peroxides. Therefore, the correct answer to the question is Option B: Potassium, rubidium, and cesium.