Chapter 8 Practice Problems [Watts, Fall 2008.]
Problem 22
(a) Having two electrons with the same spin in one orbital (the 2s orbital) is a violation of
the Pauli exclusion principle: if two electrons in the same orbital have the same spin
quantum number, they have all four quantum numbers the same, which is not allowed.
(b) Again, the Pauli exclusion principle is violated. This example has 3 electrons in one
of the 2p orbitals, and two of them have all four quantum numbers the same.
(c) There is a problem with the 3p subshell. In the most stable arrangement, i.e. the
ground state, all three 3p electrons will have the same spin: Hund’s rule says the most
stable arrangement maximizes the number of parallel spins.
Problem 24
(a) The 2p subshell should be filled (i.e. have 6 electrons) before any electrons are put in
the 3s subshell. This example only has 2 electrons in the 2p subshell.
(b) The 3d subshell should be filled (i.e. have 10 electrons) before any electrons are put in
the 4p subshell. Also, it is customary to write the 4s occupation before the 3d.
(c) The 2p subshell should be filled before electrons are put in the 3s subshell.
Problem 26
(a) There is no such thing as a 2d orbital. Since the maximum value of l is n – 1, the first
d subshell is 3d.
(b) There is no such thing as a 3f orbital. The f subshell is 4f.
(c) The 5s subshell is filled after Kr. Then comes 4d, and then 5p. Electrons enter the 4f
subshell after the 6s subshell is filled.
Problem 28
Ar: 1s22s22p63s23p6
Al: 1s22s22p63s23p1
Ne: 1s22s22p6
