Student Question

# Predict the electronic configuration of the first excited state (the next higher energy state beyond the ground state) of Pd.

Configuration of first excited state of Pd will be [Kr] 4d9 5s1. The ground state configuration is [Kr] 4d10. Palladium is a transition element and its electronic configuration is slightly different from the norm. Instead of partially filling 4d, Pd attains higher stability by completely filling up 4d instead of 5s.

Palladium (symbol: Pd) is a transition element with an atomic number of 46. The electronic configuration for Pd in the ground state can be written as:

1s2, 2s2, 2p6, 3s2, 3p6, 3d10, 4s2, 4p6, 4d10.

or, [Kr] 4d10.

This is based on the maximum electrons that can be held in an orbital and the energy levels. For example, only 2 electrons can be present in s and 6 in p, and so on.

It is interesting to note that instead of filling 5s (and getting a configuration of 5s2, 4d8), electrons tend to migrate to 4d and completely fill it. This can be understood in terms of stability. A completely filled 4d orbital will result in higher stability as compared to an incompletely filled 4d orbital.

An excited state is different from the ground state. In an excited state, an electron will gain energy and migrate to a higher energy level. (The electron may later fall back to the ground state and release the energy it gained to migrate to a higher energy level.)

For Palladium to reach an excited state the electron will migrate from the 4d orbital to 5s orbital. This means that the electronic configuration in an excited state for Palladium can be written as:

1s2, 2s2, 2p6, 3s2, 3p6, 3d10, 4s2, 4p6, 4d9, 5s1.

It can be written using this notation as well: [Kr] 4d9 5s1. The 1s2-4p6 electron levels match that of Kr, making it an effective shorthand.

In general, you can use an energy level diagram for determining the electronic configuration of an element in its ground state or excited state. However, exceptions like the current case do exist.

Hope this helps.