Question

Comment on the possible formation of the \(\mathrm{Cl}^{2-}\) ion. Why is its formation unlikely?

Short answer

The formation of \( \mathrm{ Cl ^{2-}}\) is unlikely due to high energy requirements and resulting instability.

Step-by-step solution

Understand the Basics of Chlorine

Chlorine (\( \text{Cl\)}) is a halogen element in Group 17 of the periodic table. It has an electron configuration of \[Ne\] \3s^2 3p^5\ and needs one more electron to achieve a stable electron configuration similar to noble gases. Chlorine commonly forms a \\( \text{Cl}^{-}\) ion by gaining one electron.

Consider the \ \( \mathrm{ Cl ^{2-}} \) Ion

To form a \\( \mathrm{Cl^{2-}}\) ion, chlorine would need to gain two electrons. This requires placing an additional electron in an already filled 3p subshell. This process involves significant electron-electron repulsion and is unfavorable.

Analyze Energy Considerations

The energy required to add an electron to a negatively charged ion is high due to the repulsion between the incoming electron and the electrons already present. This makes the formation of \\( \mathrm{Cl^{2-}}\) highly energy-intensive, thus unlikely.

Evaluate Stability

The \\( \mathrm{Cl^{2-}}\) ion would have a very unstable electron configuration due to repulsion forces and high energy requirements. Nature generally favors more stable, lower-energy states, making this ion formation improbable.

Key concepts

Electron Configuration

Electron configuration refers to the distribution of electrons in an atom's orbitals. It is a fundamental concept for understanding atomic structure and behavior. Each element has a unique electron configuration that helps determine its chemical properties. Chlorine, a member of the halogen group, has the electron configuration \[1s^2 2s^2 2p^6 3s^2 3p^5\]. This shows that chlorine has 17 electrons arranged in its orbitals, with its outermost shell holding 7 electrons.
This configuration is key to its reactivity. Chlorine needs one more electron to complete its outer shell, achieving a stable configuration like noble gases. This is why chlorine typically forms the \( ext{Cl}^- \) ion. When considering the formation of a \( ext{Cl}^{2-} \) ion, the electron configuration becomes problematic. Adding a second electron forces it into a previously filled subshell, creating instability and making such formation unlikely.

Halogen Group

The halogen group consists of five elements: fluorine, chlorine, bromine, iodine, and astatine. These elements are in Group 17 of the periodic table and are known for their high reactivity. Halogens have seven valence electrons, meaning they need one additional electron to achieve a full outer shell.
Their electron configuration makes them highly electronegative, enabling them to form negative ions quite easily. For example, gaining one electron transforms a chlorine atom into a \( ext{Cl}^- \) ion. However, trying to gain two electrons to form a \( ext{Cl}^{2-} \) ion is unlikely due to elemental properties specific to the halogen group.

• They naturally stabilize by gaining a single electron.
• Double negative ions would increase instability significantly.
• Energy constraints make it even more difficult to achieve \( ext{Cl}^{2-} \).

This natural tendency to form single negative ions is consistent across the halogen group.

Electron-Electron Repulsion

Electron-electron repulsion refers to the force exerted between electrons due to their negative charges. When electrons arrange in an atom's orbitals, they tend to stay as far apart as possible to minimize repulsion. This helps define the shape and energy levels of the atom's electron cloud.
In the context of forming a \( ext{Cl}^{2-} \) ion, adding an additional electron to chlorine increases electron-electron repulsion considerably. The 3p subshell of chlorine already accommodates five electrons. Trying to add two more creates a crowded environment where electrons repel each other strongly.

• This results in significant energy costs, as more energy is required to force another electron into an already repulsive environment.
• The increased repulsion creates instability, making such ions energetically unfavorable.
• For these reasons, forming a \( ext{Cl}^{2-} \) ion is not a characteristic reaction for chlorine.

The preference is always towards achieving a more stable, lower-energy state, which in this case, is the formation of \( ext{Cl}^- \).