Question

Which of the following pairs is not isoelectronic species?

(At. no. Sm, 62; Er, 68; Yb, 70; Lu, 71; Eu, 63; Tb, 65; Tm, 69)

• A. $Sm^{2+} \space and \space Er^{3+}$
• B. $Yb^{2+} \space and \space Lu^{3+}$
• C. $Eu^{2+} \space and \space Tb^{4+}$
• D. $Tb^{2+} \space and \space Tm^{4+}$

Answer 1

Answer: (A), (D)

$Sm^{2+} \space and \space Er^{3+}$

Answer 2

Isoelectronic species refers to two atoms, ions or molecules that have the same electronic structure and the same number of valence electrons term means "equal electric" or "equal charge". Isoelectronic chemical species typically display similar chemical properties.

$Tb^{2+}$→electron=63

$Tm^{4+}$→electron=65 $(not \space isoelectronic \space)$

While $Yb^{2+}$ and $Lu^{3+}$ both will have 68 electrons. and $Eu^{2+}$ and $Tb^{4+}$ both will have 61 electrons and $Sm^{2+}$ and $Eu^{3+}$ both will have 60 electrons. So, they are isoelectronic with each other.