Question

why is the electron configuration of cr metal not 3d4 4s2? group of answer choices because cr has more than 6 electrons in its valence. because 3d orbitals are lower in energy than 4s orbitals. because electrons repel each other and a different configuration allows each electron to have its own orbital (which is more stable). none of these.

Answer 1

The electron configuration of Cr metal is not 3d4 4s2 because of the principle of preferred stability. It shifts from the 4s orbital to the 3d orbital to achieve a half-filled 3d subshell, resulting in the configuration [Ar]3d5 4s1 for Cr.

Step-by-step explanation:

The electron configuration of Cr is not 3d4 4s2 because of the principle of preferred stability. In the case of Cr and Cu, half-filled and completely filled subshells are conditions of preferred stability. Therefore, an electron shifts from the 4s orbital to the 3d orbital in order to achieve a half-filled 3d subshell, resulting in the electron configuration of [Ar]3d5 4s1 for Cr. This arrangement provides extra stability compared to a configuration with 4 unpaired electrons.

Answer 2

The electron configuration of chromium is due to the stability offered by a half-filled d-subshell, as well as minimization of electron-electron repulsion, leading to each electron having its own orbital.

Step-by-step explanation:

The electron configuration of Cr (chromium) metal is not 3d4 4s2 due to the increased stability of having a half-filled d-subshell. This stability arises because of electron-electron repulsion, which is minimized when each electron occupies its own orbital. Therefore, electrons are arranged in a way such that Cr achieves a half-filled d-subshell, leading to the observed electron configuration of 3d5 4s1. Other transition metals, like copper (Cu) and niobium (Nb), also show deviations from the expected configuration principle because of the subtle energy differences between 3d and 4s orbitals and electron repulsion effects.

When considering ions of transition metals, electrons are first removed from the 4s orbital, which is higher in energy relative to the 3d orbitals. An example can be seen in the case of the chromium ion (Cr3+), which has the configuration [Ar]3d3 because the 4s electrons are removed before the 3d electrons.