Question

If oxygen molecules, \(\mathrm{O}_{2},\) were to react with magnesium atoms, how many electrons would each magnesium atom lose? How many electrons would each oxygen atom gain? How many magnesium atoms would be needed to react with each oxygen molecule? What charges would the resulting magnesium and oxide ions have?

Short answer

Each magnesium atom loses 2 electrons, and each oxygen atom gains 2 electrons. In the reaction, 2 magnesium atoms are needed to react with each oxygen molecule. The resulting ions have the following charges: Magnesium ion (Mg2+): +2, and oxide ion (O2-): -2.

Step-by-step solution

1. Determine the electronic configuration of magnesium and oxygen

In order to determine the electrons gained and lost, we first need to recall the electronic configuration of magnesium and oxygen. Magnesium is in Group 2 of the periodic table, meaning it has 2 valence electrons with the configuration \(1s^{2} 2s^{2} 2p^{6} 3s^{2}\). Oxygen is in Group 16, meaning it has 6 valence electrons with the configuration \(1s^{2} 2s^{2} 2p^{4}\).

2. Determine the ions formed by magnesium and oxygen

Magnesium being a metal and a Group 2 element tends to lose its 2 valence electrons to have a fully filled 2p orbital, resulting in a stable configuration. Thus, magnesium forms a Mg2+ ion with the electronic configuration \(1s^{2} 2s^{2} 2p^{6}\). On the other hand, oxygen has 6 electrons in the outermost shell and needs 2 more electrons to achieve a fully filled outer shell and a stable electronic configuration. Hence, oxygen tends to gain 2 electrons, forming an O2- ion.

3. Determine the number of electrons magnesium loses and oxygen gains

From the previous step, we know that each magnesium atom loses 2 electrons to form a Mg2+ ion, and each oxygen atom needs to gain 2 electrons to form an O2- ion. Thus, each magnesium atom loses 2 electrons, and each oxygen atom gains 2 electrons.

4. Determine the number of magnesium atoms needed to react with each oxygen molecule

An oxygen molecule contains 2 oxygen atoms, and each oxygen atom gains 2 electrons. Therefore, an oxygen molecule gains a total of 4 electrons. Since each magnesium atom loses 2 electrons, we need 2 magnesium atoms to provide the 4 electrons required by the oxygen molecule.\(2 \times (\text{Mg loses 2 e-}) = \text{O}_{2} \text{ molecule gains 4 e-}\) Hence, 2 magnesium atoms are needed to react with each oxygen molecule.

5. Determine the charges of the resulting magnesium and oxide ions

As we determined earlier, a magnesium atom loses 2 electrons and forms a Mg2+ ion, while oxygen gains 2 electrons to form an O2- ion. As a result, the charges of the formed ions are: Magnesium ion: \(+2\) (Mg2+) and oxide ion: \(-2\) (O2-).

Key concepts

Electron Configuration

The concept of electron configuration is essential to understanding chemical reactions, particularly when discussing how atoms gain or lose electrons during these interactions. Electron configuration describes the distribution of electrons across the different orbitals (or energy levels) in an atom. Consider magnesium, which has an electron configuration of \(1s^{2} 2s^{2} 2p^{6} 3s^{2}\). This configuration indicates that magnesium has two electrons in its outermost shell, often referred to as valence electrons. These are the electrons involved in chemical bonding.

On the other hand, oxygen, with an electron configuration of \(1s^{2} 2s^{2} 2p^{4}\), has six valence electrons. Both elements aim to achieve a stable configuration similar to noble gases. Magnesium tends to lose electrons, while oxygen tends to gain them. Understanding these configurations helps us predict their behavior when they react.

Ion Formation

Ion formation is a fundamental principle in chemistry, where atoms transform into ions by losing or gaining electrons to achieve a more stable electronic configuration. Metals like magnesium usually lose electrons to form positive ions, known as cations. By shedding its two valence electrons, magnesium forms a \(Mg^{2+}\) ion, embodying a stable noble gas configuration with all orbitals filled up to \(2p^6\).

In contrast, nonmetals like oxygen tend to gain electrons, resulting in a negative ion, termed an anion. Oxygen gains two electrons to complete its outer shell, forming an \(O^{2-}\) ion. This stable electronic configuration mirrors that of a noble gas, emphasizing why ion formation is pivotal in chemical bonding.

• Metals form cations by losing electrons.
• Nonmetals form anions by gaining electrons.
• Noble gas configurations drive the formation of ions.

Magnesium and Oxygen Interaction

The interaction between magnesium and oxygen illustrates the power of chemical reactions resulting in the formation of ionic compounds. When magnesium atoms and oxygen molecules come together, a series of electron exchanges occur. Each magnesium atom loses two electrons, turning into a \(Mg^{2+}\) ion. Simultaneously, each oxygen atom in a \(O_2\) molecule requires two electrons, thus obtaining four electrons in total if we consider the two atoms. This means two magnesium atoms are needed to satisfy two oxygen atoms.

The chemical reaction is driven by the formation of these stable ions: magnesium provides the necessary electrons that oxygen requires. The resulting ionic compound is magnesium oxide \((MgO)\), where magnesium ions carry a charge of \(+2\) and oxygen ions have a charge of \(-2\). Both elements achieve their desired noble gas electron configurations, highlighting the theme of stability that underpins chemical reactions. This interaction exemplifies a complete transfer of electrons to form strong ionic bonds.