Simplify the following text for a Grade 7 native English-speaking person.
Original: Lithium oxide ( ( ( Lithium ) ) O ) or lithia is an inorganic chemical compound . Lithium oxide is formed along with small amounts of lithium peroxide when lithium metal is burned in the air and combines with oxygen : 4Li + â ' 2 .
Simplified: When lithium is burned to air , it forms lithium oxide .