Classification of Elements: The Periodic Table Arranging The Elements: The Russian chemist Dmitri Mendeleev uncovered evidence that consisted of a huge collection of facts about the 63 elements that had been discovered by the mid-1800's. His clues had to do with the physical and chemical properties of these elements. Mendeleev was convinced that he could arrange the elements so that those with similar properties were grouped together. Mendeleev made a card for each element including …showed first 75 words of 1244 total…

…showed last 75 words of 1244 total…the noble gases are sometimes called the inert - gases. Certain properties of elements vary in regular ways from left to right across a period. These properties include electron arrangement, reactivity, atomic size, and metallic properties. The valence number of an elements is related to the electrons in the ourter most energy level of an atom of that element. It is these electrons that are involved in the chemical combining of elements to form compounds.