Greeks (Aristotle)
Classified everything in four categories; earth, wind and fire. Maybe classified into aether (from space elements)
Greeks (Democritus)
Described the material world as tiny invisible particle. Called "atoms" uncuttable.
Dobreiner
Organized elements in groups of three (called Law of Triads)
Newlands
Created the law of octaves. Organized all the elements in groups of 7 where the 8th element repeats the chemical properties of the first. Table organized by increasing mass.
Mendeleev
Organized all elements by atomic weight and organized them by properties in families. Also left space for future elements that were undiscovered.
Moseley
Does the x ray experiment. Comes up with the Atomic #s for each proton. Also comes up with the new organization of the periodic table.
Seaborg
Decides to take the F block (bottom) out of the periodic table. He did this due to the way in which these elements reacted.
Groups (families)
the columns on the periodic table.
Periods (Series)
the rows on the periodic table (represents the energy level)
How many periods are on the periodic table?
7 periods
How many families are on the periodic table?
18 families