Question

Why is fluorine always assigned an oxidation state of \(-1 ?\) What oxidation number is \(u\) sually assigned to the other halogen elements when they occur in compounds? In an interhalogen compound involving fluorine (such as ClF), which atom has a negative oxidation state?

Short answer

Fluorine has the highest electronegativity value (3.98) on the periodic table, which means it attracts electrons more effectively than other elements. As a result, fluorine's oxidation state is always -1. Other halogens (chlorine, bromine, iodine, and astatine) exhibit various oxidation states, depending on the compound they form. In interhalogen compounds like ClF, fluorine has a negative oxidation state (-1) due to its higher electronegativity, while chlorine has a positive oxidation state (+1).

Step-by-step solution

Understand the concept of oxidation state#

Oxidation state is a concept that helps us understand the distribution of electrons within a molecule or an ion. It represents the hypothetical charge an atom would have if all its bonds to other atoms were ionic. Electronegativity plays a key role in determining the oxidation state of an element in a compound.

Explain fluorine's electronegativity and oxidation state#

Fluorine is the most electronegative element in the periodic table, with an electronegativity value of 3.98 on the Pauling scale. This means that fluorine atoms attract electron pairs more effectively than any other element when forming chemical bonds. When fluorine forms a bond with another element, it typically gains one electron, leading to a negative charge. Consequently, fluorine's oxidation state is always -1.

Discuss the oxidation states of other halogens#

The other halogen elements (chlorine, bromine, iodine, and astatine) have high electronegativity values but not as high as fluorine. As such, their oxidation states may vary depending on the compounds they form. In general, when these halogens form compounds with elements having lower electronegativity, they exhibit an oxidation state of -1. When combined with elements with higher electronegativity, their oxidation state can range from +1 to +7, depending on the specific compound.

Analyze the interhalogen compound ClF#

In an interhalogen compound like ClF (chlorine monofluoride), the elements involved are fluorine (most electronegative) and another halogen, in this case, chlorine. Since fluorine's electronegativity is higher than that of chlorine, fluorine will draw electrons towards itself, gaining a negative charge. Therefore, fluorine will have the negative oxidation state of -1 in ClF. The chlorine atom, with lower electronegativity, will instead lose an electron and have a positive oxidation state of +1.

Key concepts

Electronegativity

Electronegativity is a measure of an atom's ability to attract and hold onto electrons in a chemical bond. It plays a pivotal role in determining how atoms interact in molecules. Generally, the higher an element's electronegativity, the more it pulls electrons towards itself when forming bonds.

On the Pauling scale, which is a common method of quantifying electronegativity, values range from about 0.7 to 4.0. Fluorine is the most electronegative element with a value of 3.98, making it extremely efficient at pulling electrons from other atoms. This high electronegativity is why fluorine always takes an oxidation state of \(-1\) in compounds, as it typically gains one electron when bonding.

Understanding electronegativity helps explain why certain elements consistently have specific oxidation states. When a highly electronegative element like fluorine bonds with a less electronegative element, it pulls electrons towards itself, influencing the resulting charge or oxidation state of each atom.

Halogen Elements

Halogens are a group of elements found in Group 17 of the periodic table. This family includes fluorine, chlorine, bromine, iodine, and astatine. Characterized by high electronegativity and reactivity, halogens are diatomic molecules in their elemental form.

One striking feature of halogens is their ability to achieve an oxidation state of \(-1\) when combining with less electronegative elements, as they typically gain an electron to complete their outer shell. However, their oxidation states can vary widely, from \(-1\) to \(+7\), depending on the electronegative nature of the elements they bond with and the compound's structure.

The variation in oxidation states is particularly evident when halogens form compounds with elements of lower electronegativity or other halogens. This versatility in oxidation states makes halogens essential in forming a wide variety of chemical compounds.

• Fluorine: Always \(-1\) due to highest electronegativity.
• Chlorine, Bromine, Iodine: Vary from \(-1\) to \(+7\) depending on the compound.

Interhalogen Compounds

Interhalogen compounds consist of two or more different halogens bonded together, such as chlorine fluoride (ClF) or bromine trifluoride (BrF₃). These compounds exhibit intriguing chemistry due to the electronegativity differences between the constituent halogens.

In a compound like ClF, two halogens, chlorine and fluorine, are bonded. Since fluorine has a higher electronegativity than chlorine, it attracts electrons more strongly, giving it a \(-1\) oxidation state. Chlorine, on the other hand, assumes a positive oxidation state of \(+1\) due to its lower ability to attract shared electrons compared to fluorine.

The oxidation states in interhalogen compounds can sometimes be predicted by recognizing the order of halogens in terms of electronegativity:

• Fluorine (F)> Chlorine (Cl)> Bromine (Br)> Iodine (I)> Astatine (At)

This order helps in determining which atom in the compound will carry the negative oxidation state. Interhalogen compounds often serve as powerful oxidizing agents and demonstrate unique chemical behaviors due to the electronegativity dynamics between different halogens.