When alkali metals are heated in an excess of oxygen, the primary product formed depends on the metal itself. Match the metal with its primary metal oxide product, where M denotes the alkali metal. Oxide, M20 Peroxide, M202 Superoxide, MO2 Na Rb Li K Cs

Li = M₂O

Na = M₂O₂

K = MO₂

Rb = MO₂

Cs = MO₂

Explanation:

Since the reactivity of alkali metals increases on moving down the group with the increase in atomic size, their reactivity towards oxygen increases on going down the from lithium to caesium.

Lithium being the least reactive reacts with oxygen in the air to give white lithium oxide, LiO₂.

Sodium reacts with excess oxygen when heated to form sodium peroxide, Na₂O₂

Potassium reacts with excess oxygen when heated to form potassium superoxide, KO₂

Rubidium reacts with excess oxygen when heated to form rubidium suproxide, RbO₂

Caesium reacts with excess oxygen when heated to form caesium superoxide, CsO₂