Alkali metal oxide

A sample of sodium peroxide.

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.

• Hexarubidium monoxide (Rb₆O)
• Nonarubidium dioxide (Rb₉O₂)
• Caesium monoxide (CsO)
• Tricaesium monoxide (Cs₃O) is a dark green solid.
• Tetracaesium monoxide (Cs₄O)
• Heptacaesium monoxide (Cs₇O)
• Tricaesium dioxide (Cs₃O₂)
• Heptacaesium dioxide (Cs₇O₂)
• Undecacaesium trioxide (Cs₁₁O₃)
• Undecacaesium monorubidium trioxide (Cs₁₁RbO₃)
• Undecacaesium dirubidium trioxide (Cs₁₁Rb₂O₃)
• Undecacaesium trirubidium trioxide (Cs₁₁Rb₃O₃)

Alkali metal oxides

File:Rubidium-oxide-xtal-3D-vdW-B.png

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.

Alkali metal peroxides

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.

Alkali metal superoxides

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.

Alkali metal ozonides

• 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.
• 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.