Question

The magnetic moments of few transition metal ions are given below: metal ion magnetic moment(bm) sc3+ 0.00 cr2+ 4.90 ni2+ 2.84 ti3+ 1.73 (at no. Sc = 21, ti =22, cr = 24, ni = 28) which of the given metal ions : (i) has the maximum number of unpaired electrons? (ii) forms colourless aqueous solution? (iii) exhibits the most stable +3 oxidation state?

Answer 1

Answer:

(i) The maximum number of unpaired electrons is in $Cr^{2+}$ where n=4.

Formula used for magnetic moment :

$\mu=\sqrt{n(n+2)}$

where,

1. $\mu$ = magnetic moment  for $Sc^{3+}$=0.00 BM

n = number of unpaired electrons

$\mu=\sqrt{n(n+2)}=0.00BM$ , n=0

2. $\mu$ = magnetic moment  for $Cr^{2+}$=4.90 BM

$\mu=\sqrt{n(n+2)}=4.90BM$ , n=4

3. $\mu$ = magnetic moment  for $Ni^{2+}$=2.84BM$\mu=\sqrt{n(n+2)}=2.84BM$, n=2

4. $\mu$ = magnetic moment  for $Ti^{3+}$=1.73BM

$\mu=\sqrt{n(n+2)}=1.73BM$ , n=1

(ii) $Sc^{3+}$ forms colorless aqueous solution as it contains no unpaired electrons. The color is due to excitation of unpaired electrons.

(iii) $Sc:21:[Ar]3d^14s^2$

Thus scandium after losing three electrons , i.e $Sc^{3+}$  will have completely filled stable configuration and thus exhibits the most stable +3 oxidation state.

$Cr:21:[Ar]3d^54s^1$

$Ni:21:[Ar]3d^84s^2$

$Ti:21:[Ar]3d^24s^2$

Answer 2

Answer:

(i)Cr2+

(ii)Sc3+

(iii)Sc3+

Explanation:

(i) because it has 4 unpaired electrons

(ii)it has no unpaired electrons

(iii)no unpaired electrons