Question

Why is first ionization enthalpy of chromium lower than that of Zn?

Hint:

Half-filled d-subshells, like in chromium, provide extra stability, making ionization easier compared to elements with completely filled orbitals like zinc.

Answer 1

The first ionization enthalpy of chromium is lower than that of zinc due to electron configuration and orbital stability. Chromium's configuration is \( [Ar]\, 3d^5 4s^1 \), with a 4s electron promoted to the 3d orbital, creating a stable, half-filled d-subshell. This enhanced stability in chromium facilitates electron removal compared to zinc, whose configuration is \( 3d^{10} 4s^2 \). Zinc's completely filled d-subshell confers greater stability, thus requiring more energy for ionization. Consequently, chromium exhibits a lower first ionization enthalpy.
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