Alkali metal oxide

The alkali metals react with oxygen to form several different compounds: suboxides, oxides, peroxides, superoxides, and ozonides. They all react violently with water.

Alkali metal suboxides

Structure of undecacaesium trioxide.

Crystal structure of rubidium oxide.

Lithium oxide (Li₂O) is the lightest alkali metal oxide and a white solid. It melts at 1570°C.
Sodium oxide (Na₂O) is a white solid that melts at 1132°C and decomposes at 1950°C. It is a component of glass.
Potassium oxide (K₂O) is a pale yellow solid that decomposes at 350°C.
Rubidium oxide (Rb₂O) is a yellow solid that melts at 500°C.
Caesium oxide (Cs₂O) is a yellow-orange solid that melts at 490°C.

Crystal structure of sodium peroxide.

Lithium peroxide (Li₂O₂) is a white solid that melts at 195°C. It reacts with carbon dioxide to form lithium carbonate and oxygen and was used as a carbon dioxide scrubber on the Apollo spacecraft.
Sodium peroxide (Na₂O₂) is a pale yellow solid that melts at 460°C and boils at 657°C.
Potassium peroxide (K₂O₂) is a yellow solid that melts at 490°C.
Rubidium peroxide (Rb₂O₂) is produced when rubidium stands in air.
Caesium peroxide (Cs₂O₂) is produced by the decomposition of caesium oxide above 400°C.

Crystal structure of potassium superoxide.

Lithium superoxide (LiO₂) has only been isolated in matrix isolation at 15 K.
Sodium superoxide (NaO₂) is a yellow-orange solid that melts at 551.7°C. It is made by the high-pressure oxidation of sodium peroxide.
Potassium superoxide (KO₂) is a yellow solid that decomposes at 560°C. It is used as a CO₂ scrubber, H₂O dehumidifier and O₂ generator in rebreathers, spacecraft, submarines and spacesuit life support systems.
Rubidium superoxide (RbO₂) is produced when rubidium burns in air.
Caesium superoxide (CsO₂) is produced when caesium burns in air.

Lithium ozonide (LiO₃) is a red solid which is produced from caesium ozonide via an ion-exchange process.
Sodium ozonide (NaO₃) is a red solid which is produced from caesium ozonide via an ion-exchange process.^[1]
Potassium ozonide (KO₃) is a dark red solid which is produced when potassium is burned in ozone or exposed to air for years.
Rubidium ozonide (RbO₃) is a dark red solid which is produced when rubidium is burned in ozone.
Caesium ozonide (CsO₃) is a dark red solid which is produced when caesium is burned in ozone.^[2]

↑ Klein, W.; Armbruster, K.; Jansen, M. (1998). "Synthesis and crystal structure determination of sodium ozonide". Chemical Communications (6): 707–708. doi:10.1039/a708570b.
↑ F.A. Cotton and G. Wilkinson "Advanced Inorganic Chemistry", 5th edition (1988), p.462