[Cyrustorz]

Those periods don't even exist that far down yet so how am I supposed to count?

[Borek]

Hint: periodic table follows quantum numbers.

[Cyrustorz]

Hint: periodic table follows quantum numbers.

I'm just drawing a blank 

[Borek]

Do you know the Aufbau principle? Follow it and see when you get 170 electrons. What is the expected configuration?

[Cyrustorz]

Do you know the Aufbau principle? Follow it and see when you get 170 electrons. What is the expected configuration?

I have just tried reading through this page on Aufbau principle to see if there is something I have missed:
https://en.wikipedia.org/wiki/Aufbau_principle
I know the order in which electrons fill shells to the end of the periodic table, but I can't see anywhere such as on that wikipedia article for example that says how to extrapolate past the periodic table...  Will there be other shells beyond the F shell? I just don't understand.  We absolutely did not touch on this in class and I haven't been able to find it in my textbook either

[Borek]

Sure, there is g after f. Not that the letter used to describe it matters in any way. I will repeat the original hint: it is all in quantum numbers. Yes, for small values of the azimuthal quantum number we often use letters, so the orbital for l=0 is called s, for l=1 it is p, for l=2 it is d, but it is l that matters. Plus, we know l is lower than n. And n can take any positive, integer value.

[mikasaur]

Think of the quantum numbers and how they all relate to each other. And how the periodic table is built around these quantum numbers.

To describe an orbital you need three quantum numbers: n (principle), l (angular momentum), and m_l (magnetic). To describe the electrons in those orbitals you need a fourth quantum number: m_s (spin).

• The principle number n can take on values between 1 and ∞.
• The angular momentum number l can take on values between 0 and [itex]n-1[/itex] (and this is the quantum number that represents the shells s, p, d, f...).
• The magnetic number m_l can take on values between [itex]-l...0...l[/itex].
• The spin quantum number m_s can take on values of [itex]-\frac{1}{2}[/itex] and [itex]+\frac{1}{2}[/itex].

Each element has a unique electron configuration described by the four quantum numbers. And you can predict the electron configuration by following the rules of the Aufbau principle.

To make it easier on yourself, maybe first try some easy examples that are within the known periodic table. What would be the electron configuration of the 5th element? The 10th? What about the 100th? How do these electron configurations relate to groups?

For the 5th element we need 5 electrons, so we have:

• [itex]n=1,l=0,m_l=0,m_s=-\frac{1}{2}[/itex]
• [itex]n=1,l=0,m_l=0,m_s=+\frac{1}{2}[/itex]
• [itex]n=2,l=0,m_l=0,m_s=-\frac{1}{2}[/itex]
• [itex]n=2,l=0,m_l=0,m_s=+\frac{1}{2}[/itex]
• [itex]n=2,l=1,m_l=-1,m_s=-\frac{1}{2}[/itex]

Where was the last (5th) electron added in the example above? Which group would it be put in?

You could continue this exercise for the 170th electron, which would be tedious. Could you think of a shortcut, though? Maybe try to think of how many electrons there can possibly be for a given primary quantum number, [itex]n[/itex].