Thallium toxicity and ionocovalency
Yonghe Zhang
American Huilin Institute
Thallium (Tl) is the p electron orbital element. Its chemical properties due to the lone pair electron effect (ns2)is similar to the s electron orbital elements (alkali metals) having a strong ionic property of the unipositive valence cation.
According to the ionocovalent theory: everything exists in ionocovalent potential (IC), the harmony of the ionic energy I(Z*,Iz , n*) with the covalent environment C(rc-1, n*rc-1):
IC = I(Z*,Iz , n*) C(rc-1, n*rc-1)
From ionocovalent parameters (table below), we can see:
1) Comparing to the potassium cations K+ and Na+, the thallium cation Tl+ has the higher ionic properties I (Z *, Iz, n *) and the small covalent radius rc, therefore, thallium cations have higher ionocovalency IC: Tl+ (1.877) , Tl3+(3.307) i.e. the higher bond strength, charge density and polarizing power. Tl3+(3.307) has a strong ability to obtain electrons and is a strong oxidizing.
2) Since the ionization energy generated Tl+ is particularly low (6.11) than the ionization energy generated Tl3+ (29.8), Tl forms a more stable ionic compounds of toxicity on the body life.
3) Its high spatial covalency, n*rc-1 (2.815) enables a high affinity for sulfur ligands to attack sulfur-containing proteins
4)As the atomic covalent radius of Tl+ (1.495) is almost identical with K+ (1.95) and Na+(1.572), it can thus enter the body via potassium uptake pathways, causing life threatening processes that transport potassium and sodium are disrupted.
Ionocovalent parameters
Cations
|
n*
|
Iz
|
Iav
|
rc-1
|
n*rc-1
|
Z*
|
rc
|
Xz
|
XIC
|
IC
|
Na+
|
2.89
|
5.14
|
5.14
|
0.636
|
1.838
|
1.777
|
1.572
|
0.948
|
0.853
|
1.13
|
K+
|
3.45
|
4.34
|
4.34
|
0.513
|
1.769
|
1.949
|
1.95
|
0.899
|
0.799
|
0.999
|
Tl+
|
4.36
|
6.11
|
6.11
|
0.646
|
2.815
|
2.922
|
1.549
|
1.069
|
1.164
|
1.887
|
Tl3+
|
4.36
|
29.8
|
18.11
|
0.646
|
2.815
|
5.122
|
1.549
|
1.423
|
1.749
|
3.307
|
n* - Effective principle quantum number Iz - Ultimate IP Iav - Average IP,
Z* - Effective nuclear charge rc-1 - σ -covalency rc - Covalent radiu
Xz - Zhang electronegativity 1982 n*rc-1- Spatial covalency
XIC -Zhang electronegativity 2010 IC - Ionocovalency
[1] Zhang, Y. Ionocovalency and Applications 1. Ionocovalency Model and Orbital Hybrid Scales. Int. J. Mol. Sci. 2010, 11, 4381-4406
[2] Zhang, Y. 离子共价性 J. Am. huilin. Ins. 2011, 5 (B), 1-9
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