TlCl more stable thanTlCl3

Why is TlCl more stable than TlCl₃ molecule?

‘Tl’ is a group 13^th or p-block heavier element. The outer electronic configuration of thallium is, [Xe] 4f¹⁴ 5d¹⁰ 6s²6p¹.

From the electronic arrangement of Tl, it has been found that, the valence electron of thallium element is 3.

So, the oxidation state of Tl should be +3 . But it has been found that , +3 oxidation state of Tl is less stable than +1 state.

Because, ‘Tl’ contained inner ‘d’ or ‘f’ electrons.

Now, due to poor shielding effect of ‘d’ or ‘f’ orbitals, the effective nuclear charge on outer most ‘s’-electrons act strongly.

That is, the nucleus bind or pull the ‘s’-electrons strongly. Hence , this two ‘s’-electron remain inert and does not participate in chemical reaction.

Since +3 oxidation state of Tl is less stable than +1 oxidation state, so TlCl is more stable than TlCl₃ molecule.

Why is PbO₂ act as a strong oxidizing substance ? 

The outer electronic configuration of lead is, [Xe] 4f14 5d106s26p2.

From the electronic arrangement of lead, it has been found that, the valence electron of lead is 4. So, the oxidation number of lead should be +4 .

But it has been found that, the +4 oxidation state of lead is unstable than +2, due to inert pair effect.

For this reason, PbO2 or Pb(IV)oxide act as a strong oxidizing substance.

PbO₂ is so strong oxidizing that, it can oxidized even concentrated sulfuric acid ,nitric acid and hydrochloric acid.

Through these oxidation, lead changes its unstable oxidation state[+4] to stable oxidation state[+2 ].

Why Po(VI) compound act as a strong oxidizing substance ?

The outer electronic configuration of polonium is, [Xe] 4f¹⁴ 5d¹⁰ 6s²6p⁴.

So, the maximum oxidation state of polonium may be +6. But, it is very unstable oxidation state.

Because, the outer ‘6s’-electron of polonium have no tendency to participate in chemical reaction due to inert pair effect.

Hence, Po(VI) compound act as a strong oxidizing agent in inorganic chemistry.

That is, Po(VI) compound have great tendency to reduced the other substance, so that, it can changes its unstable +VI oxidation state to stable +IV oxidation state.

For this purpose, Po(VI) compound [ PoF₆ ] act as a strong oxidizing substance.

Why is the melting point of ‘Sb’ and ‘Bi’ elements less than ‘As’ element ?

The melting point of ‘Sb’ and ‘Bi’ elements are less than ‘As’ element.Because  of the inertpair effect, the ‘Sb’ and ‘Bi’ elements form three covalent bond instead of five. 

So, in ‘Sb’ and ‘Bi’ elements, the inter-atomic force of attraction become less than that of expected.

Hence the melting point of ‘Sb’ and ‘Bi’ elements is less than ‘As’ element.

·        Why is TlCl more stable than TlCl₃ molecule?

·        Why is PbO₂ act as a strong oxidizing substance ? 

·        Why Po(VI) compound act as a strong oxidizing substance ?

·        Why is the melting point of ‘Sb’ and ‘Bi’ elements less than ‘As’ element ? 

Octet rule definition and limitation for covalent molecule