The first ionization energy of the d-block elements are________.

• Ionisation energy is the minimum energy to remove the electron from the isolated gaseous atom.
• The ionization energy of the $\mathrm{d}$-block elements is larger than $\mathrm{s}$-block and smaller than the $\mathrm{p}$-block elements, between which, they are placed.
• In the first series, except for chromium and copper first ionization energy involves removal from the filled $\mathrm{s}$-orbital.
• Among them, the ionization energy of $\mathrm{d}$-block elements increases with the increase in atomic number up to $\mathrm{Fe}$.
• Thus, they are more electropositive than $\mathrm{p}$-block elements and less electropositive than $\mathrm{s}$-block elements.

Therefore, the first ionization energy of the $\mathrm{d}$-block elements are between $\mathrm{s}\mathrm{and}\mathrm{p}\mathrm{block}\mathrm{elements}$.