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 ns2is 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 

4As 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.

 

Ionocovalency 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     I-      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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