Question

Which of the following will form diamagnetic tripositive ions?

a. La and Ce
b. Ce and Yb
c. La and Lu
d. Eu and Lu

Answer 1

Lanthanum (La3+) and Lutetium (Lu3+) form diamagnetic tripositive ions as all their electrons are paired in their respective 3+ oxidation state.

Step-by-step explanation:

The question asks which of the listed elements will form diamagnetic tripositive ions. Diamagnetic ions have no unpaired electrons. For an ion to be diamagnetic, it must have all of its electrons paired.

Electron Configurations for Each Element and Its 3+ Ions:

• Lanthanum (La): [Xe] 5d1 6s2 - La3+: [Xe] (all electrons are paired, thus La3+ is diamagnetic)
• Samarium (Sm): [Xe] 4f6 6s2 - Sm3+: [Xe] 4f5 (has unpaired electrons, not diamagnetic)
• Lutetium (Lu): [Xe] 4f14 5d1 6s2 - Lu3+: [Xe] 4f14 (all electrons are paired, Lu3+ is diamagnetic)

Based on the electronic configurations, La and Lu both form diamagnetic ions when they are in their 3+ oxidation state, because all their electrons are paired. Therefore, the correct answer is option (c) La and Lu.