Knowing that the chemistry of lanthanoids \left ( Ln \right ) is dominated by its +3 oxidation state, which of the following statements is incorrect ?

  • Option 1)

    Because of the large size of the Ln (III) ions the bonding in its compounds is predominantly ionic in character .

  • Option 2)

    The ionic sizes of Ln (III) decrease in general with increasing atomic number.

  • Option 3)

    Ln (III) compounds are generally colourless.

  • Option 4)

    Ln (III) hydroxide  are  mainly  basic in  character  

 

Answers (1)

As we learnt in 

Ionic Radii -

As atomic radii, ionic radii also decrease with increase in atomic number.In +3 oxidation state.

 

-

 

and

 

Lanthanoid contraction -

The filling of if orbits before 5d orbits result regular decrease in atomic radii called Lanthanoid contraction or can say the size of radii not much increase.

- wherein

e.g.\:\:\:\:3d\rightarrow 4d\rightarrow 5d

 

 

Due to large size bonding of Ln\left ( III \right ) is ionic. The ionic size of Ln\left ( III \right ) decreases on increasing atomic number  i.e. due to lanthanoid contraction Hydroxide of Ln\left ( III \right ) are mainly basic in nature. Ln\left ( III \right ) compounds are generally colourless. 

 


Option 1)

Because of the large size of the Ln (III) ions the bonding in its compounds is predominantly ionic in character .

This option is incorrect.

Option 2)

The ionic sizes of Ln (III) decrease in general with increasing atomic number.

This option is incorrect.

Option 3)

Ln (III) compounds are generally colourless.

This option is correct.

Option 4)

Ln (III) hydroxide  are  mainly  basic in  character  

This option is incorrect.

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