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Ch.6 - Electronic Structure of Atoms
Chapter 6, Problem 76a

Write the condensed electron configurations for the following atoms and indicate how many unpaired electrons each has: (a) Mg.

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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 is represented using a notation that indicates the energy levels and sublevels occupied by electrons. For example, magnesium (Mg) has an atomic number of 12, leading to the electron configuration of 1s² 2s² 2p⁶ 3s², which shows how electrons fill the available orbitals.
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Unpaired Electrons

Unpaired electrons are those that occupy an orbital alone, without a partner of opposite spin. The presence of unpaired electrons is crucial for understanding an atom's magnetic properties and reactivity. In the case of magnesium, its electron configuration reveals that there are two unpaired electrons in the 3s orbital, which influences its chemical behavior.
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Hund's Rule

Hund's Rule states that electrons will fill degenerate orbitals (orbitals of the same energy) singly before pairing up. This principle helps minimize electron-electron repulsion and stabilizes the atom. Understanding this rule is essential for determining the number of unpaired electrons, as it explains why the 3s orbital in magnesium has two unpaired electrons instead of one paired electron.
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