4. What is valency? Explain different types of
valencies

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?

An observation that requires measurement is called quantitative observable or qualitative

Ineed this asap part i: scientific method what is the difference between science and pseudoscience? what is the scientific method?