chemistry

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elements known since prehistoric times

Au, Ag
industrial revolution, 1870 over ___ elements were known

70
Dobereiner

found trios of elements with similar properties.
John Newlands

arranged elements by atomic weight and found that similar elements appeared to be 7 elements apart; "Law of Octaves"
Periodic

pattern repeats in a specific manner
Meyer

Organized elements, but no attempts at predictions.
Mendeleev
- -organized periodic table
- -arranged in increasing atomic mass
- -predicted existence of 3 missing elements; Sc, Ga, and Ge
Moseley
- determined atomic numbers of the known elements and rearranged the periodic table.
- -put elements in order of atomic number not mass
the periodic table

the repetition of chemical and physical properties of elements when they arranged by increasing atomic number
elements with atomic number greater than 92 are ________

synthetic
____ make up most of the elements of the periodic table

metals
found in famalies 13-18

non-metals
characteristics of both metals and non-metals

metalloids
atoms in the same group have similar properties because..

same # of valence electrons
energy level of an elements valence electron indicates...

the period on the periodic table
valence electrons are the main source for..

elemental properties
s-block elements
- -hold 2 electrons
- -very active metals
representative elements
- -group 1A-8A
- -display a large range of chemical and physical properties
hydrogen
- group 1, 1 valence electron