IandAwere calculated as the energy difference between the neutral and the
cation and anion, respectively.
Li Ca Cb F
I 5.33 12.3 11.1 21.4
A 0.272 4.55 1.05 3.24
Mulliken
w
2.80 8.38 6.08 12.0Paulingw 0.98 2.55c 2.55c 3.98
aStarting from a neutral quintet 1s (^2) , 2s (^1) , 2px (^1) , 2py (^1) , 2pz 1
bStarting from a neutral triplet 1s (^2) , 2s (^2) , 2px (^1) , 2py (^1) , 2pz 0
cBased on experimental bond energies in C–X molecules
We see that the Mulliken and Pauling electronegativities seem to be reasonably
in step, with electronegativity increasing from Li to C to F, in accord with experi-
ence, but withAmaking quintet C more electronegative than F. EvidentlyIandA
act together to determine atomic avidity for electrons.
Electronegativity and other properties from DFT calculations have been dis-
cussed by Zhan et al. [5], and an electronegativity scale based on the energies of
neutrals and cations which correlates well with the Pauling scale has been proposed
by Noorizadeh and Shakerzadeh [6].
References
- Pauling L (1932) J Am Chem Soc 54:3570; Pauling L (1960) The nature of the chemical bond,
3rd edn. Cornell University Press, Ithaca, NY, chapter 3 - Murphy LR, Meek TL, Allred AL, Allen IC (2000) J Phys Chem A 104:5867
- Smith DW (2002) J Phys Chem A 106:5951
- Matsunaga N, Rogers DW, Zavitsas AA (2003) J Org Chem 68:3158
- Zhan C-G, Nichols JA, Dixon DA (2003) J Phys Chem A 107:4184
- Noorizadeh S, Shakerzadeh E (2008) J Phys Chem A 112:3486
Chapter 7, Harder Questions, Answers
Q7
Given the wavefunction of a molecule, it is possible to calculate the electron density
function. Is it possible in principle to go in the other direction? Why or why not?
From density functional theory, given the electron density function of a mole-
cule (and its charge and multiplicity), and a perfect functional (let’s idealize the
problem; the question does specify “in principle”) we can home in on a unique
molecule. Then we could use ab initio theory to find the wavefunction.
Answers 643