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elements known since prehistoric times
Au, Ag
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industrial revolution, 1870 over ___ elements were known
70
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Dobereiner
found trios of elements with similar properties.
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John Newlands
arranged elements by atomic weight and found that similar elements appeared to be 7 elements apart; "Law of Octaves"
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Periodic
pattern repeats in a specific manner
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Meyer
Organized elements, but no attempts at predictions.
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Mendeleev
- -organized periodic table
- -arranged in increasing atomic mass
- -predicted existence of 3 missing elements; Sc, Ga, and Ge
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Moseley
- determined atomic numbers of the known elements and rearranged the periodic table.
- -put elements in order of atomic number not mass
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the periodic table
the repetition of chemical and physical properties of elements when they arranged by increasing atomic number
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elements with atomic number greater than 92 are ________
synthetic
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____ make up most of the elements of the periodic table
metals
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found in famalies 13-18
non-metals
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characteristics of both metals and non-metals
metalloids
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atoms in the same group have similar properties because..
same # of valence electrons
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energy level of an elements valence electron indicates...
the period on the periodic table
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valence electrons are the main source for..
elemental properties
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s-block elements
- -hold 2 electrons
- -very active metals
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representative elements
- -group 1A-8A
- -display a large range of chemical and physical properties
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hydrogen
- group 1, 1 valence electron
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