Question

Which of the following pairs has the same size?

Options

• Fe²⁺, Ni²⁺

• Zr⁴⁺, Ti⁴⁺

• Zr⁴⁺, Hf⁴⁺

• Zn²⁺, Hf⁴⁺

Answer 1

Zr⁴⁺, Hf⁴⁺

Explanation:

Zirconium (Zr) and Hafnium (Hf) belong to the same group in the periodic table. Hafnium (Hf) comes after the lanthanoids, and due to lanthanoid contraction, the size of Hf⁴⁺ becomes almost equal to Zr⁴⁺. So, both Zr⁴⁺ and Hf⁴⁺ have almost the same ionic radius, even though Hf has more protons.