Special Electronic Configurations

[lkh1986]

I ony know how to explain the anomality of Cr and Cu's electronic configurations.

And in the assignments, I am asked the following:
(a) For Rh: Why not [Kr]4d7 5s2 but [Kr] 4d8 5s1
(b) For Ir: Why not [Xe]4f14 5d8 6s1 but [Xe] 4f14 5d7 6s2

Can someone give a brief explanation? Thanks.

 

[Gokul43201]

We can help you, but only if you first show us some of your own effort or ideas. Please read the posting guidelines.

Also, we would need to know what class this is for and what topic was last covered in this class (before this problem was posed).

 

[Blueshift5]

The electronic configurations of elements are based on the arrangement of electrons in an atom's energy levels or orbitals. In general, the electronic configuration follows the Aufbau principle, which states that electrons fill orbitals in order of increasing energy. However, there are some exceptions to this rule, such as the anomalous electronic configurations of Cr and Cu.

These elements have a partially filled d orbital, which is more stable than a partially filled s orbital due to the repulsion between electrons in the same orbital. Therefore, in order to achieve a more stable configuration, one electron from the s orbital moves to the d orbital, resulting in the anomalous configurations of [Ar] 3d5 4s1 for Cr and [Ar] 3d10 4s1 for Cu.

Now, let's look at the cases of Rh and Ir. In the case of Rh, the electronic configuration is [Kr] 4d8 5s1 instead of the expected [Kr] 4d7 5s2. This is because the 4d orbital is closer in energy to the 5s orbital, making it more stable to have one electron in each orbital rather than two in the 5s orbital.

Similarly, for Ir, the electronic configuration is [Xe] 4f14 5d7 6s2 instead of the expected [Xe] 4f14 5d8 6s1. Again, this is due to the stability of having one electron in each orbital rather than two in the 6s orbital.

In summary, the anomalous electronic configurations of Cr and Cu, as well as the configurations of Rh and Ir, follow the principle of maximum stability, where electrons are arranged in a way that minimizes repulsion and maximizes stability. This results in the observed electronic configurations for these elements.