Name: ______Hr: ____
Orbital Diagrams and Quantum Numbers
Modified from www.gcisd-k12.org/cms/lib/TX01000829/.../quantum%20numbers.doc and kentchemistry.com
Aufbau Principle - electrons fill orbitals starting at the lowest available energy state before filling higher states (1s before 2s).
Pauli Exclusion Principle - An orbital can hold 0, 1, or 2 electrons only, and if there are two electrons in the orbital, they must have opposite (paired) spins. When we draw electrons, we use up and down arrows. So, if an electron is paired up in a box, one arrow is up and the second must be down. Therefore, no two electrons in the same atom can have the same set of four Quantum Numbers.
incorrect; electrons must spin in opposite directions
correct; the electrons have opposite spins
Hund’s Rule - When filling sublevels other than s, electrons are placed in individual orbitals before they are paired up. Electrons fill like people do on a bus. You would never sit right next to someone you did not know if there are free seats available, unless of course all the seats are taken then you must pair up.
Orbital Diagram Questions:
1. Which electron configuration represents a violation of the Pauli Exclusion Principle?
A) B)
C) D)
2. Which electron configuration represents a violation of Hund's rule for an atom in its ground state?
A) B)
C) D)
3. The correct order of increasing energy of atomic orbitals is?
A) 5p<4f<6s<5d B) 5p<6s<4f<5d C) 4f<5p<5d<6s D) 5p<5d<4f<6s
4. The orbital diagram in which both Pauli’s Exclusion Principle and Hund’s rule are violated (2s and 2p orbitals shown):
5. Electrons would first enter into which orbital?
A) 5s B) 3s C) 3p D) 4f
6. Which one of the following is the correct electron configuration for a ground-state nitrogen atom?
A) B)
C) D)
Quantum Numbers
This is our final way to describe the location of an electron. It consists of four numbers that act as coordinates to locate the electron’s position. These numbers will refer only to the element’s highest energy electron because the others fall into the same locations that have been described in the elements preceding it.
1. Principle Quantum Number (n) is Energy Level (Shell).
o Indicates distance from the nucleus
a. How do you determine n?
b. Possible values of n?
2. Second Quantum Number (ℓ) is the electron SUBSHELL
a. Indicates the shape of the region.
i. Spherical - ______
ii. Dumbbell - ______
iii. Double dumbbell donut - ______
iv. “Fancy” - ______
b. How do you determine ℓ ?
c. Possible values of ℓ ?
3. Magnetic Quantum Number (mℓ) is the electron ORBITAL
a. Indicates the orientation of the region in space
b. How do you determine mℓ ?
c. Possible values of mℓ ?
4. Spin Quantum Number (ms):
a. When two electrons are in a magnetic field, they will align opposite of one another (same as the up and down arrows). This is called the “spin”.
b. The electrons within an orbital must have opposite spins to overcome their repulsion.
c. How do you determine ms ?
d. Possible values of ms ?
Quantum Numbers Practice Problems
Fill in the orbital notation (arrows) below, then write the four quantum numbers which describe the location of the highest energy (last) electron of the following elements:
Element / 1s / 2s / 2p / 3s / 3p / 4s / 3d / Quantum Numbers1. Al
2. Ne
3. P
4. Fe
5. Mg
6. Be
Give the four quantum numbers which describe the location of each of the following:
7. The 4th electron in carbon______
8. The 25th electron in Mn______
9. The 57th electron in Ho______
10. The 49th electron in Xe______
Identify the element whose highest energy electron would have the following four quantum numbers:
11. 3, 1, -1, +1/2______
12. 4, 2, +1, +1/2______
13. 6, 1, 0, -1/2______
14. 4, 3, +3, -1/2______
15. 2, 1, +1, -1/2______
Which of the following represents a permissible set of quantum numbers? (answer “yes” if permissible and “no” if no permissible). If no, state why the set won’t work.
16. 2, 2, +1, -1/2______
17. 5, 1, 0, +1/2______
18. 6, 3,-2, +1/2______
19. 7, 0, 0, -1/2______
20. 4, 1, 8, +1/2______