5.1: Covalent Bond Formation and Strength (Problems)
- Page ID
- 112688
PROBLEM \(\PageIndex{1}\)
Which bond in each of the following pairs of bonds is the strongest?
a. C–C or \(\mathrm{C=C}\)
b. C–N or
c. \(\mathrm{C≡O}\)
d. H–F or H–Cl
e. C–H or O–H
f. C–N or C–O
- Answer a
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\(\mathrm{C=C}\)
- Answer b
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\(\mathrm{C≡N}\)
- Answer c
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\(\mathrm{C≡O}\)
- Answer d
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H–F
- Answer e
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O–H
- Answer f
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C–O
PROBLEM \(\PageIndex{2}\)
When a molecule can form two different structures, the structure with the stronger bonds is usually the more stable form. Use bond energies to predict the correct structure of the hydroxylamine molecule:
- Answer
-
The greater bond energy is in the figure on the left. It is the more stable form.
PROBLEM \(\PageIndex{3}\)
Use principles of atomic structure to answer each of the following:1
a. The radius of the Ca atom is 197 pm; the radius of the Ca2+ ion is 99 pm. Account for the difference.
b. Given these ionization values, explain the difference between Ca and K with regard to their first and second ionization energies.
Element | First Ionization Energy (kJ/mol) | Second Ionization Energy (kJ/mol) |
---|---|---|
K | 419 | 3050 |
Ca | 590 | 1140 |
c. The first ionization energy of Mg is 738 kJ/mol and that of Al is 578 kJ/mol. Account for this difference.
- Answer a
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When two electrons are removed from the valence shell, the Ca radius loses the outermost energy level and reverts to the lower n = 3 level, which is much smaller in radius.
- Answer b
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Removal of the 4s electron in Ca requires more energy than removal of the 4s electron in K because of the stronger attraction of the nucleus and the extra energy required to break the pairing of the electrons. The second ionization energy for K requires that an electron be removed from a lower energy level, where the attraction is much stronger from the nucleus for the electron. In addition, energy is required to unpair two electrons in a full orbital. For Ca, the second ionization potential requires removing only a lone electron in the exposed outer energy level.
- Answer c
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In Al, the removed electron is relatively unprotected and unpaired in a p orbital. The higher energy for Mg mainly reflects the unpairing of the 2s electron
Contributors
Paul Flowers (University of North Carolina - Pembroke), Klaus Theopold (University of Delaware) and Richard Langley (Stephen F. Austin State University) with contributing authors. Textbook content produced by OpenStax College is licensed under a Creative Commons Attribution License 4.0 license. Download for free at http://cnx.org/contents/85abf193-2bd...a7ac8df6@9.110).
- Adelaide Clark, Oregon Institute of Technology
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