Chem1000A
Spring 2005
Assignment 12 - Solutions
Practice assignment; this assignment will not be graded.
(Use SI units, show unit conversions throughout your calculations)
1. How many 3d orbitals exist? Draw all of the 3d orbitals.
There are five 3d orbitals.
x
x
z
x
y
z
y
dxy
dxz
dyz
x
y
z
dx2-y2
dz2
2. Give the electron configuration of Xe (xenon) in (a) the spectroscopic notation, (b) the orbital box
notation, and (c) the noble gas notation.
(a) Xe: 1s2 2s2 2p6 3s2 3p6 4s23d10 4p65s2 4d10 5p6
(b) Xe:
↑↓
↑↓
1s
2s
↑↓
5s
↑↓ ↑↓ ↑↓
2p
↑↓ ↑↓ ↑↓↑↓ ↑↓
4d
↑↓
3s
↑↓ ↑↓ ↑↓
3p
↑↓
4s
↑↓ ↑↓ ↑↓ ↑↓ ↑↓
3d
↑↓ ↑↓ ↑↓
4p
↑↓↑↓ ↑↓
5p
(c) Xe: [Xe] or [Kr] 5s2 4d10 5p6
3.Give the electron configuration of the following ions and their neutral parent atoms using the
spectroscopic notation.
(a) Co2+
(b) Ru4+
(c) Pb4+
First write down the electron configuration of the neutral parent element.
(a) Co2+
Co: 1s2 2s2 2p6 3s2 3p6 4s23d7
Co2+: 1s2 2s2 2p6 3s2 3p6 4s03d7
(b) Ru4+
Ru: 1s2 2s2 2p6 3s2 3p6 4s23d10 4p65s2 4d6
Ru4+: 1s2 2s2 2p6 3s2 3p6 4s23d10 4p65s0 4d4
(c) Pb4+
Pb: 1s2 2s2 2p6 3s2 3p6 4s23d10 4p65s2 4d105p6 6s2 4f14 5d10 6p2
Pb4+: 1s2 2s2 2p6 3s2 3p6 4s23d10 4p65s2 4d105p6 6s0 4f14 5d10 6p0
1-3
4. What is an orbital?
An orbital is a wavefunction of an electron, a function that describes the electron as a standing
matter wave.
5. What is an electron spin?
The electron spin is causing a magnetic moment of an electron. The magnetic moment can be thought
of arising from the spinning of an electron around its axis. Quantum mechanics tells us that we have
two possible orientations for the magnetic moment: spin-up and spin-down, represented by the
magnetic spin quantum number ms.
6. Give the electron configuration of Cr using the noble gas notation. Discuss the exceptional electron
configuration using Hund’s rule.
Chromium has a half filled 3d subshell and a half-filled 4s orbital. Both types of orbitals are that
close in energy that we have to consider Hund’s rule. Hund’s rule states that the most stable electron
configurations is that with a maximum number of unpaired electrons in degenerate orbitals, all with
the same spin direction. Strictly speaking, Hund’s rule is only valid for degenerate orbitals, i.e.,
orbitals of the same energy. However, the 4s and 3d orbitals are very close in energy and Hund’s
rule has to be applied in this case.
7. Draw the Lewis structure of NO+, include all resonance structures (only paired electrons).
+ ..
:N O
:N O +
:
..
8. Describe the bonding situation in the NO+ cation using VB theory: (a) What is the hybridization of
nitrogen and oxygen in this molecule, (b) describe the orbitals involved in the formation of the
multiple bonds in this ion. (c) How many σ and how many π bonds do you have in the NO+ cation.
(d) Draw an energy level diagram indicating the hybridization of the nitrogen, starting from the
atomic orbitals yielding the hybrid orbitals.
a) Nitrogen and oxygen in NO+ are sp hybridized.
(b) A σ bond is formed by overlap of an sp hydrid orbital on nitrogen with one sp hybrid orbital on
oxygen. One π bond is formed by overlap of the px orbital on nitrogen and the px orbital on oxygen
(the molecular axis is taken as the z-axis). The second π bond is formed by overlap of the py orbital on
nitrogen and the py orbital on oxygen.
(c) One σ bond and two π bonds are present between N and O in the NO+ cation.
(d)
E
↑ ↑ ↑
↑ ↑
2p
px py
↓↑ ↑
sp
↓↑
2s
9. The Lewis structures of salicylic acid, acetic anhydride, aspirin, and acetic acid are given below
(lone pairs are not included). Indicate the hybridization of every carbon and oxygen atom in these
compounds.
2-3
Salicylic acid:
sp3
..
acetic anhydride:
aspirine:
sp3
..
H O:
sp2
..
H O:
O:
sp2 C
sp2
H
O
.. :
sp2
sp2
sp2
sp2
sp2
sp3
sp3
CH3
sp2
sp3
CH3
sp2
C .. C
O
:O
:
..
O
..
.. sp2
sp2
acetic acid:
H3C
sp3
sp2
..sp2
O:
C
:OH
..
sp3
3-3
sp2
sp2C
sp2
sp2
sp2
..sp2
O:
H
sp3
..
H
O
.. sp2 C sp3
sp2 C
H
sp2 :O :
sp2