Thallium toxicity and ionocovalency

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*,I_z , n*) with the covalent environment C(r_c^-1, n*r_c^-1):

 

IC = I(Z*,I_z , n*) C(r_c^-1, n*r_c^-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 r_c, 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*r_c^-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       I_z -        Ultimate IP                I_av - Average IP，

         Z* - Effective nuclear charge                         r_c^-1 -     σ -covalency            r_c -  Covalent radiu          

         Xz - Zhang electronegativity 1982                 n*r_c^-1-  Spatial covalency              

         X_IC -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