Question

Ti , Zr and Hf arrange them in ionisation enthalpy ​

Answer 1

Hf>Ti>Zr arrange in ionization enthalpy

Answer 2

The increasing order of the ionization energies of the given elements is Zr<Ti<Hf.

• Zirconium, titanium, and hafnium belong to d-block and are transition metals.
• All the three elements belong to the same group. Generally down the group, ionization energy decreases due to an increase in the size of the atoms.
• But in the case of transition metals, there are some exceptions.
• In this case, Ionization energy decreases from titanium to zirconium but hafnium has higher ionization energy than both Zr and Ti.
• This can be explained by taking into consideration the Lanthanide contraction, due to which the size of zirconium and hafnium remain almost the same.
• Lanthanide contraction is the decrease in atomic size with increasing atomic number in lanthanides due to the poor shielding effect of the f-subshell.
• Thus in hafnium although there is a large increase in the number of nucleons, the size remains almost the same as compared to zirconium. Thus the nuclear attraction on the outermost electron is more in Hafnium and so the ionization energy.