To determine if the ions Mn²⁺, Fe³⁺, and Co²⁺ are isoelectronic, we first need to find the electron configurations of each ion.
1. Manganese (Mn²⁺): Manganese has an atomic number of 25. The electron configuration for neutral manganese is [Ar] 3d5 4s2. When it loses 2 electrons to become Mn²⁺, it loses the two 4s electrons. Thus, the configuration becomes [Ar] 3d5.
2. Iron (Fe³⁺): Iron has an atomic number of 26. The neutral iron configuration is [Ar] 3d6 4s2. Iron loses three electrons (two from the 4s and one from the 3d), resulting in the configuration [Ar] 3d5 for Fe³⁺.
3. Cobalt (Co²⁺): Cobalt has an atomic number of 27. Its neutral configuration is [Ar] 3d7 4s2. Losing two electrons from the 4s shell gives Co²⁺ a configuration of [Ar] 3d7.
Now let’s summarize the configurations:
- Mn²⁺:
[Ar] 3d5 - Fe³⁺:
[Ar] 3d5 - Co²⁺:
[Ar] 3d7
From the configurations, we can see that both Mn²⁺ and Fe³⁺ are isoelectronic because they both have the same electron configuration of [Ar] 3d5. However, Co²⁺ is not isoelectronic with them as it has a different configuration of [Ar] 3d7.
In conclusion: Mn²⁺ and Fe³⁺ are isoelectronic, while Co²⁺ is not isoelectronic with them.