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Periodicity Notes.notebook
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February 06, 2019
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Topic 3 PERIODICITY
The periodic table organizes elements by atomic number and by the energy level where the valence electrons for that atom are found
This arrangement also shows patterns or trends in physical and chemical properties among elements in the same rows and columns
Periodicity Notes.notebook
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February 06, 2019
Jan 307:42 AM
Using text book, make a brief summary of how each of the following scientists contributed to the development of the periodic table.
J.W. Dobereiner
J.A.R. Newlands
Dmitri Mendeleev
Henry Moseley
Jan 307:45 AM
J.W. Dobereiner (1780 1849) LAW OF TRIADS (1817) Link between atomic weight and different elements with similar properties groups of three
Ca, Sr, Ba were a triad by his law
J.A.R. Newlands (1837 1898) LAW OF OCTAVES (1865) when elements were arranged in order of atomic weight, properties of elements seemed to repeat every 8th element (thus the name octaves). This meant the group (octave) had 7 elements, and then properties began repeating. This idea was limited to certain groups (period 2 and 3) eventually mistakes appeared, with copper and silver being grouped with the alkali metals. Newlands idea was rejected and ridiculed by the Chemical Society in England, so he gave up the idea and returned to his job as chief chemist at a sugar plant.
Periodicity Notes.notebook
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February 06, 2019
Jan 712:36 PM
Dmitri Mendeleev (1834 1907) THE PERIODIC LAW (1869)
When elements are arranged in order of atomic weight, a repeated
pattern of their properties was found
Only 62 elements had been discovered
He left gaps in the table to make sure elements with similar properties were in the same rows/columns, unlike Newlands and Dobereiner. He made predictions about the properties of the missing elements.
Some of these missing elements were later discovered (gallium in
1875, scandium in 1879, germanium in 1886, and technetium in 1937) and found to have properties like the ones he predicted!
Jan 712:39 PM
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Periodicity Notes.notebook
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February 06, 2019
Jan 308:03 AM
Henry Moseley (1887 1915) THE MODERN PERIODIC LAW (1913) when the elements were arranged in order of increasing atomic numbers (Z), their properties recurred periodically. Moseley studied the wavelengths of Xrays produced in an X ray tube and found that the wavelength was characteristic of the metal used as the anode. It turned out that the wavelength depended upon the number of protons in the nucleus of the atom and was always the same for a given element. Moseley thus discovered the concept of atomic number. Moseley was sent to serve as a foot soldier in WWI, where he was killed at age 28. The British government later restricted scientists to noncombatant duty in WWII because of this.
Jan 712:49 PM
Periodicity Notes.notebook
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February 06, 2019
Jan 712:55 PM
Metals, NonMetals, and Metalloids
Nonmetals are found on the top right
poor conductors, brittle, dull, can be solids/liquids/ or gases
Metals are the largest chunk of the table, on the left hand side
good conductors, lustrous, high melting point and density, usually solids, malleable, ductile
Metalloids are found along a "staircase" that divides the two sections, and they usually have physical properties similar to metals and chemical properties similar to nonmetals
Jan 712:59 PM
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February 06, 2019
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Jan 712:54 PM
