Question

determine which of the following has the highest ionization energy. write out the full name. zr or hf

Explanation:

Step1: Consider periodic trends

In general, as we move down a group in the periodic table, the ionization - energy decreases due to the increase in atomic size and shielding effect. However, for elements in the d - block, the lanthanide contraction affects the properties of elements after lanthanum. Zirconium (Zr) is in the fifth period and Group 4, and hafnium (Hf) is in the sixth period and Group 4.

Step2: Analyze lanthanide contraction

The lanthanide contraction causes the atomic radius of Hf to be almost the same as that of Zr, while the nuclear charge of Hf is much greater. So, it is harder to remove an electron from Hf.

Answer:

Hafnium (Hf)