Chemistry 224H
Some Quantum Considerations
November 20, 2006
Oregon State University
Dr. Richard L Nafshun
1. [Review from Friday] A student
obtains a red laser pointer. The wavelength
of the red light is 660 nm. What is the speed of the red light? What is the
frequency of the red light? What is the energy of one red light photon? What is the
energy of one mole of red light photons? A student obtains a blue laser pointer.
What is the speed of the blue light? Which has a longer wavelength, the red light
or the blue light? Which has the higher frequency, the red light or the blue light?
Which has the greater energy, the red light or the blue light? Give the relative
positions of red and blue light on the electromagnetic spectrum (light). Place the
following labels on the spectrum: high energy, low energy, high frequency, low
frequency, long wavelength, short wavelength.
2.
Discuss the Bohn Model of the Hydrogen Atom.
3.
Discuss the Bright Line Spectra for Hydrogen. Show the 434.1 nm line corresponds to
the n=5 to n=2 transition.
4.
Which is higher in energy, the n=2 to n=1 transition or n=3 to n=2 transition? Higher
frequency? Longer wavelength?
5.
Discuss the photoelectric effect.
6.
Discuss quantum numbers.
Which of the following sets of quantum numbers is not valid?
(A)
(B)
(C)
(D)
(E)
n = 1, l = 0, ml = 0, ms = +½.
n = 3, l = 1, ml = 0, ms = +½.
n = 3, l = 2, ml = -2, ms = -½.
n = 2, l = 1, ml = 0, ms = +½.
n = 1, l = 1, ml = 1, ms = +½.
Discuss the statement, "Solutions to the wave equation for the hydrogen atom solved by
Schrödinger led to the new concept of the quantization of energy and space for the
electron?"
Suggest a set of four quantum numbers describes the orbital pictured below?
7.
Discuss the statement, "deBroglie’s proposition regarding the nature of matter was all
matter exhibits a wavelength: λ = h/mv."
8.
What is the wavelength of a 145 gram baseball traveling at 40 m/s (near 90 mph)?
9.
How many unpaired electrons in a ground-state (A) oxygen atom, (B) nitrogen atom,
(C) oxide ion, (D) fluoride ion, (E) calcium atom, (F) calcium ion, (G) silver ion?
10.
Determine the ground-state electron configuration of a (A) nitrogen atom,
(B) nitrogen ion, (C) aluminum ion, (D) silver ion.
11.
Consider S, As, F, Sn, and Cs. Which atom has the smallest atomic size?
12.
Consider Li+ and Li. Consider O2-, and O. Which of the following statements is correct?
(A)
(B)
13.
Li+ is larger than Li.
O2- is larger than O.
Consider a carbon atom in the ground-state. Which of the following statements is false?
(A)
(B)
(C)
(D)
(E)
The carbon atom has 6 electrons; 2 are core electrons and 4 are valence electrons.
The valence electrons in the carbon atom are all located in 2p orbitals.
The core electrons in the carbon atom are all located in the 1s orbital.
There are two unpaired electrons in the carbon atom.
The carbon atom is paramagnetic.
14.
Discuss the ramifications of the splitting of d-electron energy levels.
15.
Consider S, As, F, Sn, and Cs. Which atom has the greatest electronegativity?
16.
What are the trends in electronegativity, ionization energy, atomic size, and electron
affinity?
17.
Discuss the trends in successive ionization energies:
Successive ionization energies in kJ/mol
Element First Second Third Fourth Fifth
Sixth Seventh
Na
496
4,560
Mg
738
1,450 7,730
Al
577
1,816 2,744 11,600
Si
786
1,577 3,228
4,354 16,100
P
1,060
1,890 2,905
4,950
6,270 21,200
S
999.6
2,260 3,375
4,565
6,950
8,490
11,000
Cl
1,256
2,295 3,850
5,160
6,560
9,360
11,000
Ar
1,520
2,665 3,945
5,770
7,230
8,780
12,000
The ionization energy can be calculated by:
where n is the number of electrons missing from the ion; a0 is the Bohr radius; Z is the atomic
number; ke is the kinetic energy.
According to 2002 CODATA (Committee on Data for Science and Technology), the Bohr radius
has a value of 5.291772108(18)×10−11 m (i.e., approximately 53 pm or 0.53 ångströms). The
number in parentheses (18) denotes the uncertainty of the last digits. This value can be computed
in terms of other physical constants:
where:
is the permittivity of free space
is the reduced Planck's constant
is the electron rest mass
is the elementary charge
is the speed of light
is the fine structure constant
18.
Discuss "effective nuclear charge" and the trends:
Down the Periodic Table (Top to Bottom)
Effective Nuclear Charge stays the same for elements, going down the Periodic Table. This is
because elements have:



More Protons - More Protons = Greater Force of electrostatic attraction
Greater Distance between the nucleus and the electrons - Distance = Less force of
electrostatic attraction
Greater Shielding of electrons, since there are more electrons - More Electrons = More
Shielding = Greater Repulsion
The increase in repulsion is greater than the increase of electrostatic attraction due to the Protons;
Thus Zeff decreases going down the Periodic Table.
The effective nuclear charge is the total protons minus all electrons excluding the valence
electrons.
Across the Periodic Table (Left to Right)
Effective Nuclear Charge generally increases for elements, going across the Periodic Table.
Elements have:




Slightly More Protons
Slightly More Electrons
Same Distance
Same Shielding since electrons are just added on to the current level
The increase in the electrostatic force provided by the protons is greater than the increase in
repulsion due to shielding and distance. Therefore, across the Periodic Table, Effective Nuclear
Charge increases.
These trends can be used to explain other trends between elements. Properties such as atomic
radius, Melting and Boiling Points, electronegativity and ionization energy can be discussed
using the Effective Nuclear Charge theory.
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