Question
Explain magnetic properties of transition element.
✓
Answer
→ When a magnetic field is applied to substances, mainly two types of properties magnetic behaviour are observed : diamagnetism and paramagnetism
→ Diamagnetic substances are repelled by the applied field while the paramagnetic substances are attracted.
→ Substances which are attracted very strongly are said to be ferromagnetic.
→ In fact, ferromagnetism is an extreme form of paramagnetism. Many of the transition metal ions are paramagnetic.
→ Paramagnetism arises from the presence of unpaired electrons, each such electron having a magnetic moment associated with its spin angular momentum and orbital angular momentum.
For these, the magnetic moment is determined by the number of unpaired electrons and is calculated by using the 'spin-only' formula, i.e.,
$
\mu=\sqrt{n(n+2)}
$
→ where $n=$ is the number of unpaired electrons $\mu=$ magnetic moment in units of Bohr magneton $( BM )$.
→ The magnetic moment increases with the increasing number of unpaired electrons.
Calculated and Observed Magnetic Moments (BM)
→ Diamagnetic substances are repelled by the applied field while the paramagnetic substances are attracted.
→ Substances which are attracted very strongly are said to be ferromagnetic.
→ In fact, ferromagnetism is an extreme form of paramagnetism. Many of the transition metal ions are paramagnetic.
→ Paramagnetism arises from the presence of unpaired electrons, each such electron having a magnetic moment associated with its spin angular momentum and orbital angular momentum.
For these, the magnetic moment is determined by the number of unpaired electrons and is calculated by using the 'spin-only' formula, i.e.,
$
\mu=\sqrt{n(n+2)}
$
→ where $n=$ is the number of unpaired electrons $\mu=$ magnetic moment in units of Bohr magneton $( BM )$.
→ The magnetic moment increases with the increasing number of unpaired electrons.
Calculated and Observed Magnetic Moments (BM)
| Ion | Configuration | Unpaired Electron(s) | Magnetic moment | |
| Calculated | Observed | |||
| $Sc ^{3+}$ | $3 d^0$ | 0 | 0 | 0 |
| $Ti ^{3+}$ | $3 d^1$ | 1 | 1.73 | 1.75 |
| $Ti ^{2+}$ | $3 d^2$ | 2 | 2.84 | 2.76 |
| $V ^{2+}$ | $3 d^3$ | 3 | 3.87 | 3.86 |
| $Cr ^{2+}$ | $3 d^4$ | 4 | 4.90 | 4.80 |
| $Mn ^{2+}$ | $3 d^5$ | 5 | 5.92 | 5.96 |
| $Fe ^{2+}$ | $3 d^6$ | 4 | 4.90 | 5.3 – 5.5 |
| $Co ^{2+}$ | $3 d^7$ | 3 | 3.87 | 4.4 – 5.2 |
| $Ni ^{2+}$ | $3 d^8$ | 2 | 2.84 | 2.9 – 3,4 |
| $Cu ^{2+}$ | $3 d^9$ | 1 | 1.73 | 1.8 – 2.2 |
| $Zn ^{2+}$ | $3 d^{10}$ | 0 | 0 | |
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