Biology Class 9 Chapter 3 Periodic Table and Periodicity of-Properties

How many elements were known by the end of 18th century? How many elements were known by the end of 19th century? Elements combine to form? By 1925, the total elements known were? How many total elements are known today? Which one of the following is the discoverer of atomic number? The atomic number was discovered in? Who believed first that everything was made up of elements? In which century, John Dalton proposed his atomic theory? John Dalton theory brought a great progress in the subject of? Empedocles was a ___ philosopher? Who thought elements the building blocks of all materials? The term element was coined by?

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