a) Give a reason for each of the following :
i) The spin only magnetic moment of $ ext{Sc}^{3+}$ is zero. (1)
ii) Alloys are readily formed by transition metals. (1)
b) Write the structure of manganate ion $( ext{MnO}_4^{2-})$. (1)

Question

a) Give a reason for each of the following :
i) The spin only magnetic moment of $	ext{Sc}^{3+}$ is zero. (1)
ii) Alloys are readily formed by transition metals. (1)
b) Write the structure of manganate ion $(	ext{MnO}_4^{2-})$. (1)

Accepted Answer

![Figure — Part (b) asks to write the structure of the manganate ion MnO4^2-, which is exactly the canonical tetrahedral](/figures/the-d-and-f-block-elements/tetrahedral-manganate-ion-green-ball-and-stick-structure-sec-4-4-1.svg)

> [!TLDR]
> $	ext{Sc}^{3+}$ is $d^0$ so $\mu=0$; transition metals form alloys because of similar atomic sizes; $	ext{MnO}_4^{2-}$ is tetrahedral.

**(a)(i) Spin-only magnetic moment of $	ext{Sc}^{3+}$ is zero.**
Scandium (Z = 21) is $[	ext{Ar}]3d^1 4s^2$. On forming $	ext{Sc}^{3+}$ it loses the two $4s$ and one $3d$ electron, giving $[	ext{Ar}]3d^0$. With **no unpaired electrons** ($n = 0$),
$$\mu = \sqrt{n(n+2)} = \sqrt{0} = 0\ 	ext{BM}$$

**(a)(ii) Alloys are readily formed by transition metals.**
Transition metals have **nearly the same atomic radii** (small, comparable sizes across a series). Hence the atoms of one transition metal can easily replace the atoms of another in the metallic crystal lattice, producing solid-solution alloys.

**(b) Structure of the manganate ion $	ext{MnO}_4^{2-}$.** …

Number of unpaired electrons ( $n$ )	$\mu$ (Bohr magnetons)
1	$\sqrt{3} \approx 1.73$
2	$\sqrt{8} \approx 2.83$
3	$\sqrt{15} \approx 3.87$
4	$\sqrt{24} \approx 4.90$
5	$\sqrt{35} \approx 5.92$

Q.a) Give a reason for each of the following :

Concept understanding — Magnetic Properties of Transition Metals

Magnetic Properties of Transition Metals

The Intuition: Why Do Some Metals Get Pulled Into a Magnetic Field?

The Precise Statement

How to Use It: A Quick Table

A Common Mistake to Avoid …

Q.a) Give a reason for each of the following :

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