In this section, we calculate the energies of the neutral and cation species for Group 1A, Group 7A, and Period 2 elements and use equations (1) and (2) to determine IEs. We then plot the results along with experimental values to compare. We will use Hartree Fock theory with a DZP basis, which allows us to calculate energies of Group 1A elements up to cesium and Group 7A elements up to iodine. (For more accurate methods, see for example DensityFunctional, MP2, or Parametric2RDM. If desired, change AOmethod and AObasis in the Initialize subsection. Make sure the AObasis exists for the elements of interest.)
The following Maple input is divided into steps. The first 3 steps are used to calculated the IE of the H atom. Step 4 requires you to repeat Steps 1 - 3 to calculate IEs for the remaining elements in Group 1A. Once you have completed the series, you can plot the results and then repeat the process for Group7A and Period 2. For logistical reasons, we consider the following variables to be specified before each calculation:
Group1A series has n = 6 elements. The index m labels which atom:
H (m = 1),
Li (m = 2),
Na (m = 3),
K (m = 4),
Rb (m = 5), and
Cs (m = 6).
Num_neutral = 1, Num_cation = 0.
Group7A series has n = 4 elements. The index m labels which atom:
F (m = 1),
Cl (m = 2),
Br (m = 3), and
I (m = 4).
Num_neutral = 1,
Num_cation = 2.
Period 2 series has n = 8 elements. The index m labels which atom:
Li (m = 1),
Be (m = 2),
B (m = 3),
C (m = 4),
N (m = 5),
O (m = 6),
F (m = 7), and
Ne (m = 8).
Num_neutral = varies according to ground electron configuration and Hund's Rule,
Num_cation = varies according to ground electron configuration and Hund's Rule.
Step 1: Specify parameters
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Step 2: Calculate energies of neutral atom and cation. Determine highest occupied atomic orbital.
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Step 3: Calculate IE (in kJ/mol) using Equations (1) and (2)
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Step 4: Repeat steps 1 - 3 for each element in group or period
Step 5: Plot Ionization Energies and Compare
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How do ionization energies compare with experimental values using Equations (1)?
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Answer
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We see that for the Hartree Fock method and the DZP basis, the trend in IE is correct, but as atomic number increases, the agreement decreases.
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Repeat Steps 0 - 5 for Group 7A and Period 2.
How do ionization energies and trends compare with experimental values?
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Answer
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For both Group 7A and Period 2, the trend in calculated ionization energies compares well with experiment!
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