Question

Which of the following pair is not isoelectronic species?
$(At.no.Sm,62;Er,68;Yb,70;Lu,71;Eu,63;Tb,65;Tm,69)$

• A. $T{b}^{2+}$ and $T{m}^{4+}$
• B. $Y{b}^{2+}$ and $L{u}^{3+}$
• C. $S{m}^{2+}$ and $E{r}^{3+}$
• D. $E{u}^{2+}$ and $T{b}^{4+}$

Answer 1

Answer: (A), (C)

$S{m}^{2+}$ and $E{r}^{3+}$

Species having same number of electrons are isoelectronic

$\begin{array}{c}Tb\to 65T{b}^{+2}\to 63\text{electrons}\\ Tm\to 69T{m}^{+4}\to 65\text{electorns}\end{array}\}\text{not isoelectronic}$

$\begin{array}{c}S{m}^{+2}\to 60\text{electrons}\\ E{r}^{+3}\to 69\text{electorns}\end{array}\}\text{not isoelectronic}$