Question

The central-field approximation is more accurate for alkali metals than for transition metals such as iron, nickel, or copper. Why?

Short answer

The electron in transition metal in comparison of alkali metal is slightly different. The outmost orbit of transition metal has more than one electron so the inner electron do not completely screen the charge of the nucleus but in alkali metal have only one electron in outermost orbit so the inner electron do not completely screen the charge of the nucleus.

Step-by-step solution

Definition of metals

The term metal may be defined as the element have loss one electron.

Explain the reason of question

The electron in transition metal in comparison of alkali metal is slightly different. The outmost orbit of transition metal has more than one electron so the inner electron do not completely screen the charge of the nucleus but in alkali metal have only one electron in outermost orbit so the inner electron do not completely screen the charge of the nucleus.

Hence, the central-field approximation is more accurate for alkali metals than for transition metals such as iron, nickel, or copper.