The first row transition series are from scandium to zinc. The differentiating electrons go into 3d-orbitals.
Electronic Configuration of the First- Row Transition Elements:
| Elements | Symbol | Atomic number | Electronic configuration |
| Scandium | Sc | 21 | 1s2 2s2 2p6 3s2 3p6 4s2 3d1 |
| Titanium | Ti | 22 | 1s2 2s2 2p6 3s2 3p6 4s2 3d2 |
| Vanadium | V | 23 | 1s2 2s2 2p6 3s2 3p6 4s2 3d3 |
| Chromium | Cr | 24 | 1s2 2s2 2p6 3s2 3p6 4s1 3d5 |
| Manganese | Mn | 25 | 1s2 2s2 2p6 3s2 3p6 4s2 3d5 |
| Iron | Fe | 26 | 1s2 2s2 2p6 3s2 3p6 4s2 3d6 |
| Cobalt | Co | 27 | 1s2 2s2 2p6 3s2 3p6 4s2 3d7 |
| Nickel | Ni | 28 | 1s2 2s2 2p6 3s2 3p6 4s2 3d8 |
| Copper | Cu | 29 | 1s2 2s2 2p6 3s2 3p6 4s1 3d10 |
| Zinc | Zn | 30 | 1s2 2s2 2p6 3s2 3p6 4s2 3d10 |
Zinc with the outermost electron 4s2 3d10 is not a transition elements because it does not possess partially filled d-orbitals.
Copper atom and copper ion 4s1 3d10 which have completely filled d-orbital cannot be regarded as transition elements.
From the table above:
24Cr – [Ar] 4s1 3d5
29Cu – [Ar] 4s1 3d10
Note that some of these configurations may be unexpected – for instance, chromium and copper. To increase stability, they will have just one electron in the 4s orbital so that they can have either five (Cr) or ten (Cu) electrons in their 3d orbitals, which give a more stable configuration.There is a great stability attached when all the 3 d-orbitals are singly or doubly filled as in chromium and copper respectively.
Scandium ion Sc3+ cannot be considered as a transition element because it has no electron in the d-orbital.
Only elements that form ions with partially filled d-orbitals are classed as transition elements.
Responses