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 because of the electron configuration and the stability of the orbitals. Chromium has an electron configuration of \( [Ar]\, 3d^5 4s^1 \), where one electron from the 4s orbital is promoted to the 3d orbital, leading to a half-filled stable d-subshell. This arrangement provides extra stability to chromium, making it easier to lose an electron compared to zinc, which has a completely filled \( 3d^{10} 4s^2 \) configuration. The completely filled d-subshell in zinc results in higher stability, which makes it harder to ionize. Hence, chromium’s first ionization enthalpy is lower.
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