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Due to its functional architecture, ADOMAH Periodic Table provides the most convenient and
logical way of deriving electron configurations.
The ADOMAH PT, also known as Tetrahedral Periodic Table, reflects electron configuration of 120th element, just count number of elements in each column
vertically and you will get number of electrons in electron shells:
2-8-18-32-32-18-8-2.
Same thing can be done for any element with atomic number less than 120. Simply ignore all elements that have
greater atomic number than the element you selected and count remaining elements in each vertical column (straight
down).
For example, if you want to write electron configuration of Er(68), cross out elements 69 through 120,
as shown on diagram below , and count all remaining elements in each vertical column. You will get:
2-8-18-30-8-2. You can also divide the electrons in order of subshells s, p, d and f if you count all the
elements that were not crossed out starting at the bottom of each
column and going upward vertically:
1S2 2S2 2P6 3S2 3P6 3d10 4S2 4P6 4d10 4f12 5S2 5P6 6S2,
where first number in each group of three characters corresponds
to electron shell (column number),
the letter corresponds to the electron orbital (subshell) and the third number corresponds to number of electrons in that orbital.
If you wish to write the electron configuration in order of filling of the orbitals, follow the "cascades" and count the elements
that were not crossed out, starting at the top of each cascade and going downward, along the slanted lines:
1S2 2S2 2P6 3S2 3P6 4S2 3d10 4P6 5S2 4d10 5P6 6S2 4f12.
This is so logical and simple ! Compare this with the standard or any other Periodic Table.
To start using this simple method of deriving electron configurations,
print copy of the ADOMAH PT (PDF) HERE.
Note: it should be remembered that there are 18 common exceptions to the general rule of filling f, d and s orbitals, see below:
Cr (..., 3d5, 4s1); Cu (..., 3d10, 4s1); Nb (..., 4d4, 5s1); Mo (..., 4d5, 5s1); Ru (..., 4d7, 5s1); Rh (..., 4d8, 5s1); Pd (..., 4d10, 5s0); Ag (..., 4d10, 5s1);
La (..., 5d1, 6s2); Ce (..., 4f1, 5d1, 6s2); Gd (..., 4f7, 5d1, 6s2); Au (..., 5d10, 6s1); Ac (..., 6d1, 7s2); Th (..., 6d2, 7s2); Pa (..., 5f2, 6d1, 7s2);
U (..., 5f3, 6d1, 7s2); Np (..., 5f4, 6d1, 7s2) and Cm (..., 5f7, 6d1, 7s2).
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