Coordination Chemistry and d electron numbers

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The discussion centers on predicting the number of unpaired electrons in the complex [Cr(H2O)6]3+. Participants clarify that chromium (Cr) has an atomic number of 24, leading to a d-electron configuration of 3 in the +3 oxidation state, hence it is classified as d3. The confusion arises from the initial assumption that Cr should have 4 d-electrons, but the +3 charge indicates the loss of three electrons, resulting in a d3 configuration. Additionally, the octahedral geometry of the complex influences the arrangement of these electrons in the t2g and eg orbitals. Ultimately, the correct understanding of the electron configuration and oxidation state is crucial for determining the number of unpaired electrons.
ReidMerrill
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Homework Statement


Predict the number of unpaired electrons

[Cr(H2O)6]3+

Homework Equations

The Attempt at a Solution


I under stand how to fill out the MO with the eg and t2g and all but I'm confused about determining the number of electrons.
The answers state this is an octahedral d3 but I don't know why it is d3
Cr is the 4th element in the d block so it should be d4 but since it has a charge of +3 / is missing 3 electrons it should be d1 but neither of these are correct.
 
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