when was the third mentioned composition discovered?
1787
Silicon
In 1787, Antoine Lavoisier suspected that silica might be an oxide of a fundamental chemical element, but the chemical affinity of silicon for oxygen is high enough that he had no means to reduce the oxide and isolate the element. 
what is earth? Third planet from the Sun what is its shape? Nearly spherical when did its formation start? Ga ago what is its chemical composition? Iron, oxygen, silicon, magnesium, sulphur, nickel, calcium, and aluminum, and trace amounts of other elements.
wiki:19613903
Silicon [SEP] Discovery
In 1787, Antoine Lavoisier suspected that silica might be an oxide of a fundamental chemical element, but the chemical affinity of silicon for oxygen is high enough that he had no means to reduce the oxide and isolate the element. After an attempt to isolate silicon in 1808, Sir Humphry Davy proposed the name "silicium" for silicon, from the Latin "silex", "silicis" for flint, and adding the "-ium" ending because he believed it to be a metal. Most other languages use transliterated forms of Davy's name, sometimes adapted to local phonology (e.g. German "Silizium", Turkish "silisyum"). A few others use instead a calque of the Latin root (e.g.