The Elements - Periodic Table

Mendeleev noted patterns in the combining ratios of

elements

The Elements Lithium (Li), Sodium (Na), and Potassium (K) all formed oxides in the

ratio of two atoms per oxygen atom: R 2 O

The Elements Beryllium (Be), Magnesium (Mg), and Calcium (Ca) all formed oxides in

the ratio of one atom per oxygen atom: RO

Boron (B) and Aluminum (Al) formed R 2 O 3

Carbon (C) and Silicon (Si) formed RO 2

Recognizing the patterns of combining ratios or "valency", Mendeleev created a table organized by placing
elements with similar combining ratios in the same group. He arranged the elements within a group in
order of their atomic mass.

In 1869, the

Russian chemist

Mendeleev noted

that the repeating

patterns of

behavior could be

arranged in a

sequence of

elements giving

rise to the

"Periodic Table" of

the elements.

Special thanks to Dr. Paul Karol's "Intro to Modern Chemistry" for providing much of the information on this
page.

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Mendeleev's Table

http://pearl1.lanl.gov/periodic/mendeleev.htm (1 of 2) [5/17/2001 4:06:55 PM]