The INTERNET Database of Periodic Tables
There are hundreds of periodic tables in web space, but there is only one comprehensive database of periodic tables & periodic system formulations. If you know of an interesting periodic table that is missing, please contact the database curator: Dr Mark R Leach.
Dalton's Postulates About The Elements
Around the year 1803 in Manchester, John Dalton gave a series of lectures in which he presented his postulates:
- Elements are made of tiny particles called atoms.
- The atoms of a given element are different from those of any other element, and the atoms of different elements can be distinguished from one another by their respective relative atomic weigh/mass.
- All atoms of a given element are identical.
- Atoms of one element can combine with atoms of other elements to form chemical compounds, and a given compound always has the same relative numbers of types of atoms.
- Atoms cannot be created, divided into smaller particles, nor destroyed in the chemical process, and a chemical reaction simply changes the way atoms are grouped together.
From a very early notebook from around this time:
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© Mark R. Leach 1999-
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