Predict the number of unpaired electrons for each of the following.
(a) Sc³⁺
(b) Co²⁺

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Determine the electron configuration of the neutral atom for each element.

For Scandium (Sc), the atomic number is 21, so the electron configuration is [Ar] 3d^1 4s^2.

For Cobalt (Co), the atomic number is 27, so the electron configuration is [Ar] 3d^7 4s^2.

Remove electrons according to the charge of the ion. For Sc^3+, remove three electrons from the outermost orbitals, resulting in [Ar].

For Co^2+, remove two electrons from the outermost orbitals, resulting in [Ar] 3d^7. Determine the number of unpaired electrons in the 3d subshell.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Electron Configuration

Electron configuration describes the distribution of electrons in an atom's orbitals. It follows the Aufbau principle, which states that electrons fill lower-energy orbitals first. Understanding the electron configuration of an element is crucial for predicting its chemical behavior, including the number of unpaired electrons.

Unpaired Electrons

Unpaired electrons are those that occupy an orbital alone, without a partner of opposite spin. The presence of unpaired electrons in an atom influences its magnetic properties and reactivity. Atoms with unpaired electrons are often paramagnetic, while those with all electrons paired are diamagnetic.

Transition Metals and Oxidation States

Transition metals can exhibit multiple oxidation states due to their ability to lose different numbers of d electrons. The oxidation state affects the electron configuration and, consequently, the number of unpaired electrons. For example, Scandium (Sc) in the +3 oxidation state loses three electrons, while Cobalt (Co) in the +2 state loses two, altering their electron configurations.

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