When alkali metals (Group 1 elements) burn in excess air, they form different oxides based on their size and stability of the resulting compound. The key factor is the size of the cation: smaller cations stabilize normal oxides, while larger cations stabilize peroxides or superoxides.

Step 1: Understand the trend
As we move down the group from Lithium (Li) to Potassium (K), the atomic size increases. This affects the type of oxide formed:

• Lithium (Li) is the smallest and forms the normal oxide, Li₂O.
• Sodium (Na) is larger and forms the peroxide, Na₂O₂.
• Potassium (K) is even larger and forms the superoxide, KO₂.

Step 2: Chemical Reactions
The combustion reactions in excess air are: $4\mathrm{Li}+O2\to 2\mathrm{Li}2O$ (Lithium oxide)
$2\mathrm{Na}+O2\to \mathrm{Na}2O2$ (Sodium peroxide)
$K+O2\to \mathrm{KO}2$ (Potassium superoxide)

Step 3: Match with Options
Comparing with the given options, the correct combination is Li₂O, Na₂O₂, and KO₂.

Final Answer: The correct option is: Li₂O, Na₂O₂ and KO₂

Related Topics & Formulae

Stability of Oxides: The stability of peroxides and superoxides increases down the group due to larger cation size, which better accommodates larger anions (O₂^2- for peroxide and O₂^- for superoxide).

Important Compounds of Alkali Metals: This topic covers oxides, hydroxides, carbonates, and other salts, emphasizing their formation, properties, and uses.

Chemical Reactions of s-Block Elements: Includes reactions with oxygen, water, hydrogen, and halogens, highlighting trends and anomalies.