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In the beginning……. Dmitri Mendeleev. Mendeleev wanted to help students learn the elements that they had. So he organized them by mass. From this he started to see periodic trends for elements. (A repetition of characteristics). Mendeleev.
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Dmitri Mendeleev • Mendeleev wanted to help students learn the elements that they had. • So he organized them by mass. • From this he started to see periodic trends for elements. (A repetition of characteristics)
Mendeleev • He was able to predict elements that had yet to be discovered with his periodic table. • He predicted that elements would fit into the gaps of atomic mass that were missing.
H. G. J. Moseley • Worked in Ernest Rutherford’s laboratory • He discovered the atomic number • Then he saw that arranging the elements by atomic number allowed the groupings to represent the characteristics of the elements better than the atomic mass.
Why did atomic mass not work? Think…..difference C-12 and C-15 What is this called?
Electron shielding • The interference caused by e- in inner energy levels • Decreases attraction between nucleus to valence electrons Mrs. Matt’s board drawing….