Question

How many alkali metals on reaction with excess o2 to give superoxide?

Answer 1

The answer is potassium , rubidium and caesium.

Answer 2

Answer:

Three alkali metals: Potassium, Rubidium, and Caesium.

Explanation:

Alkali metals are the group I elements such as:

• Lithium (Li),
• Sodium (Na)
• Potassium (K)
• Rubidium (Rb)
• Caesium (Cs)
• Francium (Fr)

They belong to the s-block and are also called the Lithium Family. These elements are highly reactive with oxygen, forming a variety of oxides.

Metal oxides with the general formula $MO_{2}$ are known as superoxides.

When sodium reacts with too much oxygen, sodium peroxide is more likely to develop. When lithium reacts with too much air, it normally forms lithium oxide, but lithium peroxide can also develop.

However, when potassium, rubidium, and cesium react with too much oxygen, they produce superoxide.

• Large cations include $K^{+}$, $Rb^{+}$, and $Cs^{+}$, while superoxide ions are larger than oxide and peroxide ions.
• A large cation stabilizes a large anion due to higher lattice energies, hence these metals form superoxides.