Thallium toxicity and ionocovalency hl382013-06-06 00:49:12

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   due to the presence of empty 5d-orbitals, and so thallium may 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