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.
The Modern Periodic Table
The modern periodic table is
based on quantum numbers and blocks, here.
A periodic table can be constructed
by listing the elements by n and l quantum
The problem with
this mapping is that the generated sequence is not continuous with
respect to atomic number atomic number, Z: Check out
the sequence Ar to K, 18 to 19.
a French chemist who first published in the formulation in 1929, the Janet
or Left-Step Periodic Table uses a slightly different mapping:
While the Janet periodic
table is very logical and clear it does not separate metals from non-metals
as well as the Mendeleev version, and helium is a problem chemically.
However, it is a simple mapping
to go from the Janet or Left-Step periodic table to a modern formulation
of Mendeleev's periodic table:
On this page web, "full"
f-block included periodic tables are shown wherever possible, as above.
However, the periodic table
is usually exhibited in book and on posters in a compressed form
with the f-block "rare earths" separated away from the s-block,
p-block and d-block elements:
However, the compression used
introduces the well known problem known as a "fence
The effect is that:
La and Ac: move
from f-block to d-block
Lu and Lr: move from p-block to f-block
elements can be fitted in and classified either way. Many
thanks to JD for pointing the situation
with the periodic table is a fence post error.
Mark Winter's Web Elements
project, here, uses the formulation
Interestingly, the IUPAC
periodic table separates out 15 lanthanides, La-Lu, and 15 actinides,
Ac-Lr by leaving gaps in period 3 under Sc & Y:
This corresponds to:
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|Periodic Table, What is it showing?
© Mark R. Leach 1999-
Queries, Suggestions, Bugs, Errors, Typos...
If you have any:
Suggestions or periodic table representations not shown on this page
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