The alkali metals react with oxygen to form several different compounds: suboxides, oxides, peroxides, sesquioxides, superoxides, and ozonides. They all react violently with water.
Alkali metal suboxides
Alkali metal oxides
- Lithium oxide (Li<sub>2</sub>O) is the lightest alkali metal oxide and a white solid. It melts at 1570 ðC.
- Sodium oxide (Na<sub>2</sub>O) is a white solid that melts at 1132 ðC and decomposes at 1950 ðC. It is a component of glass.
- Potassium oxide (K<sub>2</sub>O) is a pale yellow solid that decomposes at 350 ðC.
- Rubidium oxide (Rb<sub>2</sub>O) is a yellow solid that melts at 500 ðC.
- Caesium oxide (Cs<sub>2</sub>O) is a yellow-orange solid that melts at 490 ðC.
Alkali metal peroxides
- Lithium peroxide (Li<sub>2</sub>O<sub>2</sub>) is a white solid that melts at 195 ðC. It reacts with carbon dioxide to form lithium carbonate and oxygen.
- Sodium peroxide (Na<sub>2</sub>O<sub>2</sub>) is a pale yellow solid that melts at 460 ðC and decomposes at 657 ðC.
- Potassium peroxide (K<sub>2</sub>O<sub>2</sub>) is a yellow solid that melts at 490 ðC.
- Rubidium peroxide (Rb<sub>2</sub>O<sub>2</sub>) is produced when rubidium stands in air.
- Caesium peroxide (Cs<sub>2</sub>O<sub>2</sub>) is produced by the decomposition of caesium oxide above 400 ðC.
Alkali metal sesquioxides
Alkali metal superoxides
Alkali metal ozonides
- Lithium ozonide (LiO<sub>3</sub>) is a red solid which is produced from caesium ozonide via an ion-exchange process.
- Sodium ozonide (NaO<sub>3</sub>) is a red solid which is produced from caesium ozonide via an ion-exchange process.
- Potassium ozonide (KO<sub>3</sub>) is a dark red solid which is produced when potassium is burned in ozone or exposed to air for years.
- Rubidium ozonide (RbO<sub>3</sub>) is a dark red solid which is produced when rubidium is burned in ozone.
- Caesium ozonide (CsO<sub>3</sub>) is a dark red solid which is produced when caesium is burned in ozone.
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