Question

Which of the ions show positive Borax Bead test and has the largest ionization energy:

• A. \( \text{Zn}^{2+} \)
• B. \( \text{Fe}^{3+} \)
• C. \( \text{Fe}^{2+} \)
• D. \( \text{Co}^{2+} \)

Hint:

For the Borax Bead Test, remember that transition metal ions like \( \text{Fe}^{3+} \) and \( \text{Co}^{2+} \) often show characteristic colors due to their electronic transitions, and the ionization energy tends to increase with higher oxidation states.

Answer 1

The Correct Option is B

Step 1: Borax Bead Test.
The Borax Bead Test is used to detect metal ions based on their behavior when heated with borax. Some metal ions show a characteristic color change when heated in the flame, indicating the presence of certain metals. - \( \text{Zn}^{2+} \): This ion does not give a positive result for the Borax Bead Test. - \( \text{Fe}^{3+} \): This ion gives a positive result in the Borax Bead Test, typically forming a reddish-brown color when heated. - \( \text{Fe}^{2+} \): This ion also gives a positive result, but the coloration is different from that of \( \text{Fe}^{3+} \). - \( \text{Co}^{2+} \): This ion can also give a positive result in the Borax Bead Test, showing a blue color.
Step 2: Ionization Energy.
Ionization energy is the energy required to remove an electron from an atom or ion. Higher ionization energy corresponds to a greater tendency to hold onto its electrons. Among the ions listed: - \( \text{Zn}^{2+} \) has a relatively low ionization energy.
- \( \text{Fe}^{3+} \) has the highest ionization energy due to the greater positive charge on the ion, which results in a stronger attraction between the nucleus and the electrons.
- \( \text{Fe}^{2+} \) has a lower ionization energy compared to \( \text{Fe}^{3+} \).
- \( \text{Co}^{2+} \) has a moderate ionization energy.

Step 3: Conclusion.
\( \text{Fe}^{3+} \) shows the positive Borax Bead test and has the largest ionization energy among the options provided. Final Answer: (B) \( \text{Fe}^{3+} \)