The Quantum Model - KEY
1. Which electron in chlorine has more energy, an electron in a 3s orbital or an electron in a 3p
orbital? Explain. A 3p electron will have more energy as electrons in the “p” sublevels have
more energy than “s” sublevel electrons provided that the principle quantum number is the
same.
2. Explain why the nuclear charge experienced by a 2s electron of boron is greater than that for
the 2p electron. A 2s electron will be closer to the nucleus than a 2p electron; therefore the
force from the nucleus will be greater.
3. Two electrons in an atom both occupy the 1s orbital. What quantity must be different for the
two electrons? What principle governs the answer to this question? The ms must be different
because the Pauli Exclusion Principle states that in order for two electrons to occupy the same
orbital, they must be spinning in opposite directions.
4. What quantum numbers must be the same in order for orbitals to be degenerate (have the
same energy)? Explain. “n” and “l” must be the same. “n” indicates energy level and “l”
indicates type of sublevel. In order for electrons to have the same energy, they must be in the
same sublevel.
5. In the Bohr model of the hydrogen atom the electron orbits the nucleus at a radius of 0.53 Å
(angstroms = 10-10 m). In the quantum mechanical model of the hydrogen atom, the most
probable distance of the electron from the nucleus is 0.53 Å. Explain the significance of the
difference between these two statements. The quantum mechanical model is based on
probability and doesn’t attempt to describe the exact position of an electron.
6. For n = 4, what are the possible values of l? 0,1,2,3
7. Give the possible values for n, l, and ml for each orbital in the 2p sublevel.
2, 1, -1
2,1,0
2,1,1
8. Which of the following quantum numbers would be allowed in an atom?
(a)
n=2
l=2
ml = -2
(b)
n=4
l=3
ml = -1
(c)
n=1
l=0
ml = 0
(d)
n=6
l=3
ml = -4
For each set that is possible, write the designation for the sublevel to which the orbital
belongs.(e.g. 2s, 3p, 4f…) and for each set not possible, explain why.
(a)not possible – l = 2 indicates a d sublevel and there is not a d sublevel in the 2 nd energy level.
(b)4f
(c)1s
(d) not possible l = 3 indicates an “f” sublevel and ml for an “f” must be ≥-3 and ≤3
9. List the possible values for all four quantum numbers for a 2p electron in nitrogen.
n =2
l=1
ml = -1,0,1
ms = ½
10. List the four quantum numbers for the 44th electron in Tin.
n =4
l=2
ml = -2
ms = -½
11. What is the maximum number of electrons that can have the following quantum numbers?
(a) n = 5 and l = 3 14
(b) n = 4, l = 3 and ml = -3 2
(c) n = 4, l = 1 and ml = 1 2
12. List the four quantum numbers for the last electron in Krypton. n = 4 l = 1 ml = 1 ms = -½