Quantum Numbers and Electron Configuration Review
In-Class Worksheet
Problem 1: DO AT HOME/in down time here FOR YOURSELF: Make an organization chart, describing the rules for
quantum numbers. You can use mine/the books/and internet versions for examples, but I’d rather you design something
that is easy for you to understand. Make a cool one and hand it to me and I’ll share it with the class (don’t worry I’ll keep
you anonymous). Any really great ones ones I may post online to help your fellow students out as well. Be creative and
make this time to help yourself.
Reminder of the rules:
n= 0, 1, 2, ……..
l=
0……..n-1
ml= -l……….+l
(note those are the letter l as in Linda)
Quantum Numbers and Electron Configuration Review
Problem 2: Decide if each set of quantum numbers is allowed. If they are, state the allowed values for the missing
quantum numbers, and decide how many orbitals and how many electrons are possible. I’ll do (a) as an example.
a) n=5, l=2
b) n=4, l= 1 and 0
c) n=3, ml=1, ms=+1/2
Problem 3: Write the electron configuration for the atom listed. Then draw the electron configuration, and for each
subshell write the quantum numbers for each. I’ll do (a) as an example.
A) Nitrogen.
B) Arsenic
C) Iron
Quantum Numbers and Electron Configuration Review
Extra Study Practice with a friend: There likely won’t be time for this exercise. I wanted to include it though so those of
you that study in groups get a feel for a good way of studying this with friends.
a) Write three sets of quantum numbers. You may include some or all of the n, l, ml, ms values. Some of these should be
allowed sets, some should be not allowed (please don’t get ridiculous and also don’t be to easy, the highest n you should
deal with is 5, and they shouldn’t all be super easy questions. Think like an instructor, what would you do if you were
making an exam). Hint: always define n, even if you give n=2 or 3 like below. If you don’t the answer for how many
orbitals and how many electrons will always be infinite.
b) When prompted trade with the person next to you. (or two or three people, so long as you don’t have your own
paper).
c) For each set of quantum numbers given, decide if they are possible or impossible. Decide how many orbitals could
have these quantum numbers, and how many electrons it describes.
d) Pass it back to the original owner: check their answers. Discuss any issues you disagree on.
Example:
Person 1: writes down: n=2 or 3, l=1, ms=+1/2
Person 2: Thinks: No rules are broken so this set is allowed. Because l=1, m l can equal -1, 0, 1 for each energy level. Since this is
defined as n=2 or 3 and both energy levels are allowed to have l=-1,0,1 that means that there will be 6 orbitals (three p orbitals from
each level). Because ms was given as +1/2, only one electron in each orbital can have the assigned ms value. Therefore there are also
6 electrons.
Writes: yes, 6 orbitals, 6 electrons
Person 1: “I agree”
Person 2: “we are geniuses”
Or friendly discourse on who is correct and why if you do not agree. (If you still don’t agree post it on the facebook for all your
classmates to work on)
Quantum Numbers and Electron Configuration Review
Challenge Question: **** Taken from one of my favorite exams when I was in college and expanded upon.
You are now an interuniverse traveler. In your travels you come across universes with physical rules much different than
our own.
In one universe quantum numbers do not follow the same rules as our own universe. You speak with one of the
creatures and they explain that in their universe quantum numbers follow the rules:
n = any integer, (same as ours)
l= 0, 1, 2, up to n (note NOT the same as ours)
ml= -l….0…..l (note same as ours, except of course that l is different).
ms= - ½ , 0, ½ (NOT the same as ours). And the electrons fill according to the same Pauli Exclusion and Aufbau principles
that we have here in our own universe.
Given this set of rules. How many electrons do their first and second noble gases contain?
What is the electron configuration for something with 15 electrons.