Question

Why do scientists need to classify elements

Answer 1

because they get a guided idea of what types of elements you are working with. For example they will look near the bottom to find elements that are reactive and it helps to see which elements are easiest to react with each other. For example, if you want to make a new compound from the periodic table alone you can find out what mass of each element you need to make it work succussfully

Answer 2

Originally, the need to classify elements into families with like qualities steamed from organizational purposes. However, it was also to help find patterns in order to help predict new elements that had not yet been discovered.