Principal Quantum Number - Periodic Table

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Lauren Huang 1H
Posts: 60
Joined: Fri Sep 28, 2018 12:16 am

Principal Quantum Number - Periodic Table

Postby Lauren Huang 1H » Fri Oct 26, 2018 4:35 pm

Why is it that 3d is not on the same level as 3s and 3p on the periodic table?

ian_haliburton_1f
Posts: 61
Joined: Fri Sep 28, 2018 12:24 am

Re: Principal Quantum Number - Periodic Table

Postby ian_haliburton_1f » Fri Oct 26, 2018 4:52 pm

This is because until it has a pair of electrons occupying it, the 4s orbital actually has less energy than the 3d orbitals. So, elements whose outermost electrons are in 4s (Potassium and Calcium) occur in the table before any of the 3d elements. To include the 3d elements in the same period as 3s and 3p would mean also having to put these 4s elements there as well, so the structure is cleaner with 4s and 3d their own new period.

Nicholas Carpo 1L
Posts: 36
Joined: Fri Sep 28, 2018 12:19 am

Re: Principal Quantum Number - Periodic Table

Postby Nicholas Carpo 1L » Fri Oct 26, 2018 9:24 pm

I think it also has to do with the fact that the atomic numbers of 3d are larger than 4s so it would make more sense if they would be arranged after it, on the same row.

ie. Sc (which has a 3d orbital) has 21 protons or electrons while Ca (which only has up to 4s) has 20 protons or electrons.


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