Question

In a borax bead test under hot condition, a metal salt (one from the given) is heated at point B of the flame, resulted in green colour salt bead. The spin-only magnetic moment value of the salt is ............ BM (Nearest integer) [Given atomic number of Cu = 29, Ni = 28, Mn = 25, Fe = 26]

Answer 1

5

Answer 2

The borax bead test is used to identify certain metal ions by the color they impart to a molten borax bead. A green color bead under hot conditions at point B of the flame (typically representing the reducing flame) points towards the presence of Iron (Fe$^{2+}$). The atomic number of Iron is 26. Its electronic configuration is [Ar] 3d$^6$ 4s$^2$. In the Fe$^{2+}$ state, the electronic configuration is [Ar] 3d$^6$. The 3d orbital can accommodate 10 electrons. For 3d$^6$, the electron distribution is: $\stackrel{\uparrow \downarrow}{\text{3d}} \quad \stackrel{\uparrow}{\text{3d}} \quad \stackrel{\uparrow}{\text{3d}} \quad \stackrel{\uparrow}{\text{3d}} \quad \stackrel{\uparrow}{\text{3d}}$ There are 4 unpaired electrons (n = 4).

The spin-only magnetic moment ($\mu_s$) is calculated using the formula: $\mu_s = \sqrt{n(n+2)} \text{ BM}$ Substituting n = 4: $\mu_s = \sqrt{4(4+2)} = \sqrt{4 \times 6} = \sqrt{24} \text{ BM}$ Calculating the value: $\sqrt{24} \approx 4.898979... \text{ BM}$ The nearest integer to 4.898979... is 5. Therefore, the spin-only magnetic moment of the salt is 5 BM.