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WS Atomic Structure, Periodicity, Bonding, & IMAFs
Section II Free Response
Calculator Permitted
CLEARLY SHOW THE METHODS USED AND STEPS INVOLVED IN YOUR ANSWERS.
It is to your advantage to do this, because you may earn partial credit if you do and little or no
credit if you do not. Attention should be paid to significant figures.
1.
Answer the following questions regarding light and its interactions with molecules, atoms,
and ions.
(a) The longest wavelength of light with enough energy to break the Cl–Cl bond in Cl2(g) is 495 nm.
(i) Calculate the frequency, in s–1, of the light.
(ii)
Calculate the energy, in J, of a photon of the light.
(iii) Calculate the minimum energy, in kJ mol–1, of the Cl–Cl bond.
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(b)A certain line in the spectrum of atomic hydrogen is associated with the electronic
transition of the H atom from the sixth energy level (n = 6) to the second energy level
(n = 2).
(i) Indicate whether the H atom emits energy or whether it absorbs energy during the
transition. Justify your answer.
(ii)
The energy associated with this transition is calculated to be 4.84 x 10–19 J.
Calculate the wavelength, in nm, of the radiation associated with the spectral line.
(iii) Account for the observation that the amount of energy associated with the same
electronic transition (n = 6 to n = 2) in the He+ ion is greater than that associated
with the corresponding transition in the H atom.
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Your responses to these questions will be graded on the basis of the accuracy and relevance of
the information cited. Explanations should be clear and well organized. Examples and equations
may be included in your responses where appropriate. Specific answers are preferable to broad,
diffuse responses.
First
Second
Third
Ionization Energy
Ionization Energy
Ionization Energy
–1
–1
(kJ mol )
(kJ mol )
(kJ mol–1)
Element 1
1,251
2,300
3,820
2.
Element 2
496
4,560
6,910
Element 3
738
1,450
7,730
Element 4
1,000
2,250
3,360
The table above shows the first three ionization energies for atoms of four elements from the
third period of the periodic table. The elements are numbered randomly. Use the
information in the table to answer the following questions.
(a) Which element is most metallic in character? Explain your reasoning.
(b) Identify element 3. Explain your reasoning.
(c) Write the complete electron configuration for an atom of element 3.
(d) What is the expected oxidation state for the most common ion of element 2?
(e) What is the chemical symbol for element 2?
(f) A neutral atom of which of the four elements has the smallest radius?
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3.
Explain each of the following observations using principles of atomic structure and/or
bonding.
(a) Potassium has a lower first-ionization energy than lithium.
(b)The ionic radius of N3– is larger than that of O2–.
(c) A calcium atom is larger than a zinc atom.
(d)Boron has a lower first-ionization energy than beryllium.
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4.
Use principles of atomic structure, bonding and/or intermolecular forces to respond to each
of the following. Your responses must include specific information about all substances
referred to in each question.
(a) At a pressure of 1 atm, the boiling point of NH3(l) is 240 K, whereas the boiling point of
NF3(l) is 144 K. Account for the difference in the boiling points of the substances.
(b)The melting point of KCl(s) is 776˚C, whereas the melting point of NaCl(s) is 801˚C.
Account for the difference in the melting points of the substances.
(c) As shown in the table below, the first ionization energies of Si, P, and Cl show a trend.
Element
First Ionization Energy
(kJ mol–1)
Si
786
P
1012
Cl
1251
(i)
For each of the three elements, identify the quantum level (e.g., n =1, n = 2, etc.)
of the valence electrons in the atom.
(ii)
Explain the reasons for the trend in the first ionization energy.
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(d) A certain element has two stable isotopes. The mass of one of the isotopes is 62.93 amu
and the mass of the other isotope is 64.93 amu.
(i) Identify the element. Justify your answer.
(ii)
5.
Which isotope is more abundant? Justify your answer.
Answer the following questions based on observations of the photoelectron spectroscopy of elements.
(a) On the photoelectron spectrum for magnesium given below, draw the spectrum for aluminum.
(b)Given the photoelectron spectra below for phosphorus, P, and sulfur, S, which of the
following best explains why the 2p peak for S is further to the left than the 2p peak for P,
but the 3p peak for S is further to the right than the 3p peak for P? Circle your answer.
I. S has a greater effective nuclear charge than P, and the 3p sublevel in S has greater electron repulsions than in P.
II. S has a greater effective nuclear charge than P, and the 3p sublevel is more heavily shielded in S than in P.
III. S has a greater number of electrons than P, so the third energy level is further from the nucleus in S than in P.
IV. S has a greater number of electrons than P, so the Coulombic attraction between the electron cloud and the
nucleus is greater in S than in P.
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Answer KEY
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1999
2007 B
1997 D
2005
#2
#6
(ATOMIC THEORY)
#7
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AP® Chemistry: PES Sample Items (released Spring 2014)
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