2.85

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Hyein Cha 2I
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2.85

Postby Hyein Cha 2I » Sat Oct 28, 2017 9:16 pm

The question is:

‘In the heavier transition metal elements, especially lanthanoids and actinoids, there are numerous exceptions to the regular order of orbital occupation predicted by the building-up principle. Sugfest why more exceptions would be noted for these elements’

I have seen the the solutions manuel but I cannot understand why.. could someone please explain? Thanks!

Chem_Mod
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Re: 2.85

Postby Chem_Mod » Sat Oct 28, 2017 10:28 pm

Electrons prefer to reside in a lower energy state because less energy means more stability. When the energy spacing between two states are large (such as in n=1 to n=2), the electron will more likely follow the building up principle. However, as you move away from the nucleus, energy spacing between energy states become smaller (ex. n=5 to n=6 is a much smaller energy change than n=1 to n=2). As a result, electrons are more likely to disobey the principle when the energy spacing is small because it is not as energetically unfavorable to violate the rule.

skalvakota2H
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Re: 2.85

Postby skalvakota2H » Sat Oct 28, 2017 10:31 pm

Typically, as the occupied energy levels increase in principle quantum number, the energies move closer together, which implies that the energy is dependent on the number of electrons in the level.
However, with transition metals, this does not happen when the electrons occupy high energy levels. Hence, this change in electronic structure is what causes a rearrangement of energy pattern.

Sara Sasaki 1K
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Re: 2.85

Postby Sara Sasaki 1K » Sat Oct 28, 2017 10:36 pm

Additionally from a previous Chemistry Community post:

"As the occupied energy levels increase in principal quantum number, the energies get closer and closer together to the point that their energy DEPENDS on how many electrons in that level.

This does not happen until the transition metals, when the electrons begin to occupy these higher energy levels. For example It is the reason why 4s is filled before 3d."

Connor Kelligrew 2D
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Re: 2.85

Postby Connor Kelligrew 2D » Sat Oct 28, 2017 11:59 pm

Hello! If you remember the diagram Dr. Lavelle drew in lecture showing the different energy levels an electron in a Hyrdrogen atom can occupy, the n=1,2,3,... lines he drew correspond to the energy levels of the atomic orbitals of Hyrdogen with principal quantum numbers n=1,2,3,... Note that the energy levels get closer to each other as the value of n increases. The value of these certain discrete energies can be found from the wave function of the electron of a Hydrogen atom. The building-up principle dictates that the electrons fill the lower-energy subshells before filling higher-energy subshells, and although the energy of the subshells is simply given to us in this class, determining which subshell energy level is higher or lower comes from each respective wave function.

The problem is that the wave function can only be solved for Hydrogen, which has one electron. The calculation gets too complex for atoms with more than one electron, and is impossible to solve. Thus, the model for Hydrogen is generalized for the rest of the periodic table. As you get to elements with higher protons and electrons, this model gets less and less accurate, especially for the higher energy levels that are already close together in the model for the Hydrogen atom. The model that works for most elements fails for some, and thus experimental evidence leads us to a configuration that conflicts with the principle.

Hyein Cha 2I
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Re: 2.85

Postby Hyein Cha 2I » Fri Nov 03, 2017 6:56 am

thank you all so much! It makes sense now


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