The Bohr Atom (for hydrogen and hydrogen-like atoms)
Positive nucleus w/ electron orbiting about in a circle (m will refer to electron mass unless
noted) Classical physics says that the electron will radiate (lose energy) and fall into the
1.The first step in this problem is to convert the wavelength, , to a frequency, , and
then calculate the energy of the photon using = h. In such problems you must take
care to use a consistent set of units. We will use S.I. units. Thus,
= 18900 = 18900
Solutions to Additional Transition Metal Bonding Problems
1. Cr3+ has three d-electrons (the 4s electrons are removed before the 3d) so the electron configuration is
2. NiCl42- has tetrahedral geometry, while Ni(CN)42- has square planar geometry. Th
Radial Probability: probability of finding the electron at a distance between r and r + dr
from the nucleus.
In general, nlm (r, , ) = Radial Part x Angular Part
lm (, )
Radial Probability = Radial Probability Density x Vol
Units of k
R = k[A]
R = k[A][B]
R = k[A]2
R = k[A]3
[A] = [A]oe-kt
ln[A] vs. t
1 = 1 + kt
The problem: Our naive application of what we learned with regard to the energy
of an electron in a one-electron atom or ion does not work. For example, recall
the appropriate energy expression
En = -R Z2 /n2 where R is the Rydberg Constant = 2.
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The Schrdinger equation is written
H = E, where H is an operator and E is the energy of the system.
What is the interpretation of ?
is a property of the particle (called the wave-function of the particle) It has no
immediate physical signif
Variation of Ionization Energy with Atomic Number
For a many electron atom EPE = -<Ze2/r >
Here the brackets represent an average - we must take an average because the
electron does not remain at one fixed value of r .
Earlier, we noted that Eorb = -Ze2/2
Lewis Electron Dot Structures
For ATOMS with Z 10, such structures are governed by the OCTET RULE:
The number of BONDS formed can be determined by noting that ATOMS with Z 10 tend, when
present in molecules, to achieve a RARE GAS ELECTRONIC CONFIGURATION
LECTURE DEMONSTRATION #1 (CLOCK REACTION)
The aqueous reaction between two anions, peroxydisulfate (S2O2) and thiosulfate
(S2O2), to form sulfate (SO2) and dithionate (S4O2) anions is accelerated by iodide (I). In the
course of the reaction
LECTURE DEMONSTRATION #2
(TEMPERATURE DEPENDENCE OF k)
The Arrhenius expression for the rate constant
k = A e Ea/RT
is an empirical equation that allows us to systematize kinetic data. Here, R is the Universal
gas constant, 8.31451 J mol1 K1, T is
First Hour Exam
No books or papers are to be used. Always include units in all calculations. Show all
work to receive maximum partial credit. The awarding of full credit will require that
numerical answers be supported by a clear prese
No other books or papers are to be used. Show all work. The awarding of full credit will
require that numerical answers be supported by a clear presentation of the steps used.
Include units where appropriate.
A periodic table is append
a. (12 points) Using the following information, calculate the lattice energy for KCl.
Ionization Potential of K = 420 kJ/mole
Electron Affinity of Cl = -350 kJ/mole
Standard Heat of Formation of KCl = -440 kJ/mole
Solutions to Additional Intermolecular Forces (Liquids) Problems
1. The molecules are CH3Br, CH3-O-CH3 and H3C-OH. Br does not form hydrogen
bonds. Methanol (H3C-OH) has both an electronegative O atom and the required
OH bond. It will form hydrogen bonds.
FORMAL CHARGE IDEAS
Goal: Use of FORMAL CHARGE ideas to evaluate the RELATIVE IMPORTANCE of
the contributions which DIFFERENT RESONANCE STRUCTURES make to the
ACTUAL ELECTRONIC STRUCTURE OF THE MOLECULE.
1. Write down the Lewis Electron Dot Str
MOLECULAR GEOMETRY OR MOLECULAR SHAPE
The determination of molecular shape involves determining BOND ANGLES. We are going to
use a very simple theory of molecular shape which only requires Lewis electron dot structures and
simple electrostatic ideas; this
1. This problem illustrates how the differential rate law (DRL) can be simplified
when the concentration of one or more of the participating species remains
effectively constant during the course of the reaction.
(i) Since the