Write electron configuration of Cr and Fe(III)
Answer (1)
26th Mar, 2022
Hi,
The electron configuration of Fe is [Ar]4s2 3d6. The 4s electrons are lost before the 3d electrons are lost. Reason: All orbitals shrink when the atom becomes a cation; electron-electron repulsion would soar in a shrunken 4s orbital. The electron configuration of Fe2+ is [Ar] 3d6. The next electron is removed from the 3d subshell. The electron configuration of Fe3+ is [Ar] 3d5. The 3d subshell is now half-filled, with one electron in each of the five 3d orbitals, a very stable configuration.
Similarly, Half-filled and fully filled subshell have got extra stability. Therefore, one of the 4s2 electrons jumps to the 3d5 so that it is half-filled. This give us the (correct) configuration of:
1s2 2s2 2p6 3s2 3p6 3d5 4s1
Therefore, Electron configuration of CR is [Ar] 3d 4s¹
Hope this helps.
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