show units and working out please
- Draw the orbital energy diagram for Cobalt (Co) and circle the valence electrons in the diagram. Pay careful attention to the relative energies of your orbitals, and indicate each orbital using a line or box. Label each subshell, and complete the orbital diagram with the correct number of electrons.
The Correct Answer and Explanation is:
1. Electron Configuration and Orbital Energy Diagram for Cobalt (Co)
Step 1: Determine the number of electrons in Co.
- Atomic number of Co = 27
- Therefore, Co has 27 electrons
Step 2: Write the full electron configuration of Co:
1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d⁷
- Or in noble gas shorthand:
[Ar] 4s² 3d⁷
Step 3: Draw the Orbital Energy Diagram
Below is the orbital energy diagram with relative energies increasing from bottom to top.
Each box or line represents one orbital (can hold 2 electrons max with opposite spins ↑↓).
Energy ↑
3d: ↑↓ ↑↓ ↑ ↑ ↑ (5 orbitals, 7 electrons)
4s: ↑↓ (1 orbital, 2 electrons)
3p: ↑↓ ↑↓ ↑↓ (3 orbitals, 6 electrons)
3s: ↑↓ (1 orbital, 2 electrons)
2p: ↑↓ ↑↓ ↑↓ (3 orbitals, 6 electrons)
2s: ↑↓ (1 orbital, 2 electrons)
1s: ↑↓ (1 orbital, 2 electrons)
👉 Valence electrons (circled in diagram):
Cobalt is a transition metal, so the valence electrons are in the 4s and 3d orbitals.
- Valence electrons = 4s² 3d⁷ = 9 valence electrons
✅ Explanation
Cobalt (Co), with atomic number 27, has 27 electrons in its neutral atomic state. To determine the orbital energy diagram, we follow the Aufbau principle, which dictates the order of orbital filling based on increasing energy. According to this rule, electrons fill lower-energy orbitals (like 1s) before higher ones (like 3d and 4s).
The electron configuration of cobalt is:
1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d⁷, or using noble gas notation: [Ar] 4s² 3d⁷.
In orbital diagrams, each orbital is represented by a line or box. Each can hold two electrons with opposite spins (↑↓). We fill these orbitals following Hund’s Rule, which states that electrons fill degenerate orbitals (orbitals of the same energy) singly before pairing up. This explains why the 3d subshell in Co is filled as ↑↓ ↑↓ ↑ ↑ ↑ (total of 7 electrons across 5 orbitals).
Importantly, although the 4s orbital is filled before the 3d, the 3d orbitals are lower in energy once they contain electrons, so they are often drawn below or at similar energy to 4s in diagrams of transition metals.
Cobalt is a transition metal, meaning its valence electrons include not just those in the outermost s orbital (4s), but also in the partially filled d orbital (3d). So, Co has 9 valence electrons: two from 4s and seven from 3d.
These valence electrons are crucial in determining cobalt’s chemical behavior, including bonding, oxidation states, and magnetic properties. For instance, Co commonly exhibits +2 and +3 oxidation states by losing electrons from these orbitals. Understanding its orbital diagram helps explain cobalt’s role in catalysts, alloys, and biological systems like Vitamin B12.
