history of the periodic table the scientists behind the organization
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History of the Periodic TableThe scientists behind the
organization
Dmitri Mendeleev 1834 – 1907, Russian Arranged elements in
order of increasing atomic mass
Noticed patterns in chemical and physical properties
Arranged elements with the most similar properties side by side
Mendeleev continued There were blank spots in
the table because not all elements had been discovered
Periodic Law: Elements arranged according to their atomic masses present a clear periodicity of properties
Henry Moseley 1887 – 1915, British 1913 – determined
atomic number of elements
Rearranged periodic table according to atomic number
Went to WWI, killed at age 28
British response to Moseley’s death British government no
longer assigns scientists to combat duty in times of war
We will never know what his brilliant mind could have accomplished had he lived longer
Terms explained Atomic Mass: mass relative to carbon,
approximately the number of protons + neutrons
Atomic Number: the number of protons in a single atom of an element. In a neutral atom, the number of electrons is the same as the number of protons.
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