Question

Which of the following statements are incorrect.
I) There are five unpaired electrons in $F{e}^{+3}(z=26)$.

II) $F{e}^{+3},M{n}^{+}$ and $Cr$ all having 24 electrons have same value of the magnetic moment.
III) Copper (I) chloride is coloured salt.
IV) Every coloured ion is paramagnetic.

• A. I and II
• B. II and III
• C. III and IV
• D. I and IV

Answer 1

The correct option is B II and III

Configuration of $F{e}^{3+}:1s^{2}2s^2{p}^{6}3s^2{p}^{6}4s3d^5$. Number of unpaired electrons thus is 5. Number of electrons in Cr and $M{n}^{+}=24$ , but in $F{e}^{3+}$, the number of electrons is 23. Transition element salts are coloured when there is an unpaired electron present which gives rise to d-d transition. In CuCl there is no unpaired electron, so it is colourless. Also, every ion which is coloured must have an unpaired electron which gives rise to its paramagnetic character.