Electronic Configurations Of The D Block Elements

The oxidation states of transition metals are determined by the number of electrons they can lose from their valence shell. The maximum oxidation state is influenced by the number of available d-electrons.

- Scandium (Sc) can only exhibit oxidation states of +3 because it has only one electron in its 4s orbital and readily loses that electron.
- Titanium (Ti) can exhibit oxidation states of +2, +3, and +4, as it has more electrons available for bonding.
- Chromium (Cr) can show oxidation states of +2, +3, +6, but it doesn't reach as many oxidation states as manganese.
- Manganese (Mn) exhibits the maximum number of oxidation states, ranging from +2 to +7. This is because it has five electrons in its 3d orbitals, which can participate in bonding and give rise to a variety of oxidation states.
Manganese is unique because it can easily form multiple oxidation states due to its electron configuration, allowing it to exhibit a broad range of oxidation states.

Step 1: Manganese has a large number of available electrons in its 3d orbitals.


Step 2: The multiple oxidation states of manganese, ranging from +2 to +7, allow it to form various compounds in different oxidation states.

Compounds of transition metals are generally colored because of d-d transitions. In these compounds, the d-orbitals are split into two energy levels due to the ligand field. When electrons in the lower energy d-orbitals absorb visible light, they get excited to the higher energy d-orbitals. The wavelength of light absorbed corresponds to the energy difference between the split d-orbitals, and the remaining transmitted light gives the color of the compound. This phenomenon is common in transition metal complexes, particularly when the metal has an incomplete d-orbital configuration. The presence of ligands and the metal’s oxidation state also affect the color.

Transition elements are good catalysts due to several reasons:
1. Variable oxidation states: Transition metals can easily change oxidation states, which helps in facilitating redox reactions by acting as both electron donors and acceptors.
2. Ability to form complexes: Transition metals can coordinate with various ligands, forming complexes that are essential intermediates in catalytic processes.
3. Partial filling of d-orbitals: The presence of partially filled d-orbitals allows transition metals to interact with reactant molecules, lowering activation energies.
4. Surface area: Many transition metals have high surface area, providing more active sites for reactions to occur. These factors combined make transition metals effective in speeding up reactions without being consumed in the process.
% Solution

The first ionization enthalpy of chromium is lower than that of zinc because of the electron configuration and the stability of the orbitals. Chromium has an electron configuration of , where one electron from the 4s orbital is promoted to the 3d orbital, leading to a half-filled stable d-subshell. This arrangement provides extra stability to chromium, making it easier to lose an electron compared to zinc, which has a completely filled configuration. The completely filled d-subshell in zinc results in higher stability, which makes it harder to ionize. Hence, chromium’s first ionization enthalpy is lower.
% Solution

The general electronic configuration of d-block elements (transition metals) is given by , where represents the principal quantum number of the valence shell. This configuration reflects the filling of the d-orbitals followed by the s-orbital.

Step 1: In the d-block, the d-orbitals are filled first, followed by the s-orbital.