On exposure to air, alkali metals get tranished due to formation of oxides, hydroxides and carbonates on their surface. When heated in air or oxygen they burn vigourously forming different types of oxides depending upon the nature of the metal. The formation and stability of these metals can be explained on the basis of size of alkali metal ion and the anion. Peroxides are colourless, while superoxides are coloured. The normal oxides are basic while peroxides and superoxides act as oxidising agents.
On heating in excess of oxygen, potassium gives

Options

A. `K_(2)O`
B. `KO`
C. `K_(2)O_(2)`
D. `KO_(2)`

Explanation

To solve the question regarding the products formed when potassium is heated in excess of oxygen, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding the Reaction of Alkali Metals with Oxygen**:
- Alkali metals react with oxygen to form different types of oxides. The type of oxide formed depends on the specific alkali metal and the conditions of the reaction.

2. **Identifying the Products Based on the Metal**:
- For lithium (Li), the normal oxide formed is lithium oxide (Li2O).
- For sodium (Na), the products include sodium oxide (Na2O) and sodium peroxide (Na2O2).
- For potassium (K), we need to determine the product formed when it reacts with excess oxygen.

3. **Considering the Reactivity Trend**:
- As we move down the group in the periodic table (from lithium to potassium), the reactivity of alkali metals with oxygen increases. This means that potassium is more reactive than sodium and lithium.

4. **Determining the Type of Oxide Formed by Potassium**:
- In the case of potassium, when heated in excess of oxygen, it forms potassium superoxide (KO2). This is due to the larger size of the potassium ion, which stabilizes the larger superoxide ion (O2^-).

5. **Conclusion**:
- Therefore, when potassium is heated in excess of oxygen, it predominantly forms potassium superoxide (KO2).

### Final Answer:
Potassium forms potassium superoxide (KO2) when heated in excess of oxygen.

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