Question

For the reaction \(\mathrm{Mg}(s)+\mathrm{Cl}_{2}(g) \rightarrow \mathrm{MgCl}_{2}(s),\) illustrate how electrons are gained and lost during the reaction.

Short answer

During the reaction between magnesium (Mg) and chlorine (Cl2), Mg loses its two valence electrons from the 3s orbital to become \(Mg^{2+}\), while two chlorine atoms each gain one electron to become \(Cl^{-}\) ions. The transfer of electrons results in an ionic bond between Mg and Cl, forming magnesium chloride (MgCl2). The reaction can be summarized as: \(\mathrm{Mg}(s) + \mathrm{Cl}_{2}(g) \rightarrow \mathrm{Mg}^{2+}(s) + 2\mathrm{Cl}^{-}(s) \rightarrow \mathrm{MgCl}_{2}(s)\).

Step-by-step solution

Identify the electron configurations of each element

We first need to determine the electron configuration of magnesium and chlorine. 1. Magnesium (Mg): It has an atomic number of 12, so its electron configuration is \(1s^{2}2s^{2}2p^{6}3s^{2}\). Mg has 2 valence electrons in the 3s orbital. 2. Chlorine (Cl): It has an atomic number of 17, so its electron configuration is \(1s^{2}2s^{2}2p^{6}3s^{2}3p^{5}\). Cl has 7 valence electrons.

Visualize the electron configurations with Lewis dot structures

Now we create Lewis dot structures representing the valence electrons for each element: 1. Magnesium (Mg): Mg has two valence electrons, so the Lewis dot structure would have two dots around the Mg symbol. 2. Chlorine (Cl): Cl has seven valence electrons, so the Lewis dot structure would have seven dots around the Cl symbol.

Show the transfer of electrons

In the reaction, magnesium transfers its two valence electrons to chlorine atoms to achieve a stable electron configuration: 1. Magnesium (Mg) will lose its two valence electrons from its 3s orbital to become \(Mg^{2+}\). 2. The two electrons that are lost by magnesium are gained by two chlorine atoms. Each chlorine atom will gain one electron to become \(Cl^{-}\) ions. This process can be visualized with the final Lewis dot structures and the movement of the electrons: - Magnesium (Mg) Lewis dot structure would have no dots around the symbol because it has lost its two valence electrons. - Chlorine (Cl) Lewis dot structures (two of them) would have eight dots around the symbol because they have gained one electron each.

Identify the bond formed during the reaction

The electron transfer results in an ionic bond between magnesium and chlorine. The magnesium ions (\(Mg^{2+}\)) and chloride ions (\(Cl^{-}\)) are attracted by the opposite charges, thus forming an ionic bond and resulting in magnesium chloride (MgCl2). Overall, we have illustrated how electrons are gained and lost during the reaction between magnesium and chlorine: Mg(s) + Cl2(g) -> Mg2+(s) + 2Cl-(s) -> MgCl2(s)

Key concepts

Electron Configuration

When we dive into the world of atoms, electron configuration is like a road map. It helps us understand how electrons are arranged around an atom's nucleus. For any element, knowing its atomic number is crucial because it tells us how many protons and electrons are present. Let's take magnesium (\(\text{Mg}\)) with an atomic number of 12.
The electron configuration for magnesium is \(1s^2 2s^2 2p^6 3s^2\). Notice how magnesium's outermost orbit, or shell, holds two electrons—these are its valence electrons.
Another example is chlorine (\(\text{Cl}\)) with an atomic number of 17. Its electrons are arranged as \(1s^2 2s^2 2p^6 3s^2 3p^5\). The seven valence electrons in the outer shell are just one shy of complete stability.
Electron configurations are at the heart of chemistry because they dictate how atoms interact. Elements with nearly full or empty outer shells tend to seek electrons or lose electrons, respectively. By understanding electron configuration, we can predict and explain the chemical behaviors of different elements.

Lewis Dot Structures

Once you have the electron configuration, representing this visually using Lewis dot structures can offer clarity, especially when imagining ionic and covalent bonding. These diagrams are simple yet powerful. They show only the valence electrons involved in bonding.
For magnesium (Mg), we denote its two valence electrons by having two dots near the symbol Mg. Magnesium's \(3s^2\) electrons are ready to be given away.
For chlorine (Cl), we display seven dots to signify its seven valence electrons around the symbol Cl. It's aiming to complete its octet by attracting more electrons.
By showing these dots around element symbols, Lewis dot structures cut through complexities, making it easier for us to predict how elements might interact as they form compounds.These structures are helpful when visualizing reactions, such as the transfer of electrons during the formation of magnesium chloride.

Ionic Bonding

At the heart of ionic bonding is the exchange of electrons between atoms, leading to the creation of positively and negatively charged ions. In our magnesium chloride example, Mg gives up its two electrons to achieve a noble gas-like configuration and becomes a \(Mg^{2+}\) ion.
Each chlorine atom gains one electron. This fills their outer shell, and they become \(Cl^{-}\) ions. This electron transfer stabilizes both elements, mimicking the electron configuration of noble gases.
The attraction between the oppositely charged ions (\(Mg^{2+}\) and \(Cl^{-}\)) is what causes them to form an ionic bond. This strong electrostatic interaction results in a stable compound - magnesium chloride (\(\text{MgCl}_2\)).

• Stable compounds form because ions achieve a lower energy state.
• This type of bonding commonly occurs between metals and non-metals.
• The high melting and boiling points of ionic compounds are due to the strong ionic bonds.

In essence, ionic bonding transforms the chemical landscape, converting individual atoms into a network of ions with distinct properties.