JEE Previous Year Question

Number of colourless lanthanoid ions among the following is _______${\text{Eu}}^{3+}\text{,}{\text{Lu}}^{3+}\text{,}{\text{Nd}}^{3+}\text{,}{\text{La}}^{3+}\text{,}{\text{Sm}}^{3+}$

Topic: JEE PYQ

Answer: 2. Full step-by-step solution below.