Electronic Configuration of Co³⁺

Understanding the Electronic Configuration of Co³⁺

Cobalt is a transition metal with atomic number 27. Its electronic configuration is This means that cobalt has two electrons in its outermost 4s orbital and seven electrons in its inner 3d orbitals. When cobalt loses three electrons and becomes Co³⁺, its electronic configuration changes.

Two Possible Configurations of Co³⁺

As the question states, there are two different configurations and explanations for Co³⁺ from a variety of sources. The first possibility is that cobalt loses two 4s electrons and becomes in accordance with aufbau principle. The second possibility is that cobalt loses one 4s electron and two 3d electrons to become .

To determine which of these two configurations is correct, we need to determine the stability or energy of each configuration.

Determining the More Stable Configuration

As mentioned in the question, the more stable or lesser energy configuration will be the correct one. To determine the energy of each configuration, we can use the Aufbau principle and Hund’s rule.

Energy of Configuration

When cobalt loses two 4s electrons and becomes , it has six electrons in its 3d orbitals. According to the Aufbau principle, electrons fill lower energy orbitals first. Since the 4s orbital has a lower energy than the 3d orbital, the loss of the 4s electrons causes an increase in energy.

Using Hund’s rule, we can further determine the energy of this configuration. Hund’s rule states that electrons fill degenerate orbitals (orbitals with the same energy) singly before they pair up. This means that the six electrons in the 3d orbitals of Co³⁺ will arrange themselves as follows:

This arrangement has a high energy because the electrons are paired up in the same orbital, which creates an electron-electron repulsion.

Energy of Configuration

When cobalt loses one 4s electron and two 3d electrons to become , it has five electrons in its 3d orbitals. According to the Aufbau principle, electrons fill lower energy orbitals first. Since the 4s orbital has a lower energy than the 3d orbitals, the loss of the 4s electron causes an increase in energy.

Using Hund’s rule, we can further determine the energy of this configuration. Hund’s rule states that electrons fill degenerate orbitals (orbitals with the same energy) singly before they pair up. This means that the five electrons in the 3d orbitals of Co³⁺ will arrange themselves as follows:

This arrangement has a lower energy than the configuration because there are no pairing electrons. Additionally, the 4s electron can participate in chemical bonding, which makes this configuration more stable.

The Correct Configuration of Co³⁺

Based on the energy calculations above, the correct configuration of Co³⁺ is . This configuration has a lower energy and is more stable than the configuration.

Conclusion

When cobalt loses three electrons and becomes Co³⁺, its electronic configuration changes. There are two possible configurations for Co³⁺: and . To determine which configuration is correct, we need to determine the energy of each configuration. Based on the Aufbau principle and Hund’s rule, we can determine that the configuration has a lower energy and is more stable than the configuration. Therefore, the correct configuration of Co³⁺ is .