Which one is the right

Endeleev saw trends in the physical and chemical properties of elements when he organized them by

Here’s one way to follow the scientific method. place the missing steps in the correct position in the process

Plz choose one of the compounds from the table and explain how you know the numbers of atoms in your formula. is it possible for two different compounds to be made from the exact same two elements? why or why not? with a limited number of elements (less than 120 are known), does this mean we also have a small number of compounds or do we have a large number of compounds in this world?