Question

The only important compounds of \(\mathrm{Ag}(\mathrm{II})\) are \(\mathrm{AgF}_{2}\) and AgO. Why would you expect these two compounds to be stable, but not other silver(II) compounds such as \(\mathrm{AgCl}_{2}, \mathrm{AgBr}_{2},\) and \(\mathrm{AgS} ?\)

Short answer

AgF2 and AgO are stable because Fluorine and Oxygen have high electron affinities that result in strong ionic bonds with Silver. Other elements like Chlorine, Bromine and Sulfur have less electron affinity and thus form unstable bonds with Silver.

Step-by-step solution

Understand the role of electron affinity

Different elements have different affinities for electrons. Fluorine (F) has the highest electron affinity, meaning it attracts electrons more readily than other elements. When Ag donates an electron to F, it forms a strong ionic bond resulting in the formation of AgF2. This is why AgF2 is stable.

Understanding the Role of Oxygen

Oxygen has a high electronegativity and tends to form a -2 charge when it gains two electrons. When silver donates two electrons to oxygen, it forms a strong ionic bond, forming AgO. This is why AgO is also a stable compound.

Understand the instability of other compounds

Chlorine (Cl), Bromine (Br), and Sulfur (S) have lower electron affinity than fluorine and oxygen. This means they are less capable to attract electrons from silver to form stable ionic bonds. Hence, AgCl2, AgBr2 and AgS are not stable compounds.

Key concepts

Electron Affinity

Electron affinity refers to the amount of energy released when an atom accepts an electron. It represents how strongly an atom wants an additional electron. Some elements have a strong desire to gain extra electrons and therefore have a high electron affinity.

- **High Electron Affinity:** Fluorine (F) has the highest electron affinity of any element. It strongly attracts electrons towards itself, which is crucial for forming stable compounds like \(AgF_2\).

- **Role in Silver Compounds:** Due to its high electron affinity, fluorine can stabilize silver in the form of \(AgF_2\) by efficiently capturing the electrons that silver donates. This transfer of electrons forms a strong ionic bond.

Other elements like chlorine (Cl), bromine (Br), and sulfur (S) have a lower electron affinity compared to fluorine and thus form less stable silver compounds.

Electronegativity

Electronegativity is the ability of an atom to attract bonding electrons in a compound. It is a key factor in determining the type of bond that will form between atoms.

- **High Electronegativity:** Oxygen (O) has a relatively high electronegativity, which means it can draw electrons close to itself in a bond. This property is important because it allows oxygen to form stable ionic bonds with metals like silver.

- **Impact on Stability:** Because oxygen can effectively attract electrons, silver can form \(AgO\) by donating two electrons to oxygen. This interaction results in a strong, stable ionic bond.

- **In Comparison:** Elements with lower electronegativity values, such as chlorine, bromine, and sulfur, tend to form weaker ionic interactions with silver, leading to instability in those compounds.

Ionic Bonds

Ionic bonds form when one atom donates electrons to another atom. This exchange creates ions: one positively charged (cation) and one negatively charged (anion). Ionic bonds are generally strong and result in stable compounds if the involved elements have compatible properties.

- **Silver's Role:** In compounds like \(AgF_2\) and \(AgO\), silver (Ag) acts as a donor, giving electrons to either fluorine or oxygen, which are capable of receiving them due to high electron affinity and electronegativity respectively.

- **Formation of Stable Compounds:** Because both fluorine and oxygen can effectively attract and hold the electrons that silver donates, the ionic bonds formed in \(AgF_2\) and \(AgO\) are strong and stable.

- **Unstable Alternatives:** When silver attempts to form ionic compounds with elements like chlorine, bromine, or sulfur, the resulting bonds are not strong enough to be stable, primarily due to the lower electron affinity and electronegativity of these elements compared to fluorine and oxygen.