Question

Due to lanthanide contraction _________.

• A. $Fe,Co,Ni$ have equal size
• B. $Zr\&Hf$ have equal size
• C. All $f$-block ions have equal size
• D. All isoelectronic ions have equal size

Answer 1

Answer: (B)

• Due to lanthanide contraction, $Zr$ and $Hf$ have equal size.​
• Atomic radii of $Zr=1.6\stackrel{\circ }{A}$ and $Hf=1.59\stackrel{\circ }{A}$
• Similarly due to lanthanoid contraction, atomic size of $Nb$ and $Ta$, $Mo$ and $W$ are almost the same.
• In the lanthanide contraction the atomic radius of the element decreases with the increase in atomic number.
• On moving down the group the atomic size increases on going from first to second member of the series.
• Because of lanthanide contraction the element present in first and second transition series posses similar characteristics.