Electron Configuration of a Transition Element
- Transition metals are elements with an incomplete d-subshell that can form at least one stable ion with an incomplete d-subshell
- This definition distinguishes them from d-block elements, because scandium and zinc do not fit the definition
- Scandium only forms the ion Sc3+, configuration [Ar] 3d0
- Zinc only forms the ion Zn2+, configuration [Ar] 3d10
- The elements of the first transition series are therefore titanium to copper
Electron Configuration
- The full electronic configuration of the first d-series transition metals is shown in the table below
- Following the Aufbau Principle electrons occupy the lowest energy subshells first
- The 4s overlaps with the 3d subshell so the 4s is filled first
- Remember that you can abbreviate the first five subshells, 1s-3p, as [Ar] representing the configuration of argon( known as the argon core)
Table showing the electronic configuration of the first d-series transition elements
Element | Electronic configuration |
Ti | 1s2 2s2 2p6 3s2 3p6 3d2 4s2 |
V | 1s2 2s2 2p6 3s2 3p6 3d3 4s2 |
Cr | 1s2 2s2 2p6 3s2 3p6 3d5 4s1 |
Mn | 1s2 2s2 2p6 3s2 3p6 3d5 4s2 |
Fe | 1s2 2s2 2p6 3s2 3p6 3d6 4s2 |
Co | 1s2 2s2 2p6 3s2 3p6 3d7 4s2 |
Ni | 1s2 2s2 2p6 3s2 3p6 3d8 4s2 |
Cu | 1s2 2s2 2p6 3s2 3p6 3d10 4s1 |
- From AS Chemistry you should recall two exceptions to the Aufbau Principle, chromium and copper
- In both cases an electron is promoted from the 4s to the 3d to achieve a half full and full d-subshell, respectively
- Chromium and copper have the following electron configurations, which are different to what you may expect:
- Cr is [Ar] 3d5 4s1 not [Ar] 3d4 4s2
- Cu is [Ar] 3d10 4s1 not [Ar] 3d9 4s2
- This is because the [Ar] 3d5 4s1 and [Ar] 3d10 4s1 configurations are energetically more stable
- The electronic configurations of an iron atom and its common ions, Fe2+ and Fe3+, are shown below
- Fe atom 1s22s22p63s23p63d64s2
- Fe2+ ion 1s22s22p63s23p63d6
- Fe3+ ion 1s22s22p63s23p63d5