Question

Determine the oxidation number of sulfur in each of the following substances: (a) barium sulfate, \(\operatorname{BaSO}_{4},(\mathbf{b})\) sulfurous acid, \(\mathrm{H}_{2} \mathrm{SO}_{3},\) (c) strontium sulfide, SrS, \((\mathbf{d})\) hydrogen sulfide, \(\mathrm{H}_{2} \mathrm{~S}\). (e) Locate sulfur in the periodic table in Exercise 4.47 ; what region is it in? (f) Which region(s) of the periodic table contains elements that can adopt both positive and negative oxidation numbers?

Short answer

Sulfur's oxidation numbers: (a) +6, (b) +4, (c) -2, (d) -2. Sulfur is in Group 16 and can have variable oxidation states.

Step-by-step solution

Oxidation Number Basics

To determine the oxidation number of sulfur, remember that the sum of the oxidation numbers in a neutral compound is zero, and for a polyatomic ion, it equals the ion's charge. Common rules include assigning +1 to hydrogen, -2 to oxygen, and considering the charge of other elements based on their group.

Determine Oxidation Number in BaSO4

In barium sulfate \( \text{BaSO}_{4} \), barium is a Group 2 element, so it has an oxidation number of +2. Oxygen typically has an oxidation number of -2, and there are four oxygen atoms totaling -8. Since the compound is neutral, the sum must be zero: \(+2 + x + 4(-2) = 0\). Solve for \(x\), the oxidation number of sulfur: \(x = +6\).

Determine Oxidation Number in H2SO3

For sulfurous acid \( \text{H}_{2}\text{SO}_{3} \), each hydrogen has a +1 oxidation number, and oxygen is -2, with three oxygens for a total of -6. Setting up the equation: \(2(+1) + x + 3(-2) = 0\). Solving for \(x\) gives: \(x = +4\).

Determine Oxidation Number in SrS

In strontium sulfide \( \text{SrS} \), strontium, a Group 2 element, has an oxidation number of +2. Since the compound is neutral, sulfur's oxidation number is \(-2\) as it balances out the +2 from strontium.

Determine Oxidation Number in H2S

For hydrogen sulfide \( \text{H}_{2}\text{S} \), hydrogen has a +1 oxidation number. The equation is \(2(+1) + x = 0\). Solving gives \(x = -2\), meaning sulfur has an oxidation number of -2.

Locate Sulfur in the Periodic Table

Sulfur is found in Group 16 of the periodic table. This group is also known as the chalcogens.

Regions with Variable Oxidation Numbers

Transition metals and some p-block elements (like sulfur) can adopt both positive and negative oxidation numbers. This is due to their ability to accommodate various electron configurations.

Key concepts

Understanding Sulfur in Chemistry

Sulfur is an intriguing element that plays a vital role in chemistry. It is found in various compounds, often in oxidation states ranging from -2 to +6. Understanding these oxidation numbers is crucial for determining how sulfur behaves in reactions.
In chemical compounds, sulfur typically forms bonds with elements like oxygen and hydrogen. For instance, in barium sulfate (BaSO₄), sulfur has an oxidation number of +6. This is because the oxidation states must add up to the neutral compound's overall charge, which is zero.
Sulfur is highly versatile, capable of forming multiple oxidation states due to its ability to accept or donate electrons. This makes it significant in a wide array of chemical processes and industrial applications.

The Periodic Table and Its Organization

The periodic table is a structured layout that organizes elements based on their atomic number, electron configuration, and chemical properties. Sulfur, for example, is located in Group 16. This group is known as the chalcogens, consisting of other elements like oxygen and selenium.
Each group in the periodic table contains elements with similar properties and valence electron configurations. This organization allows chemists to easily predict the behavior of elements during chemical reactions.
Understanding the periodic table's organization is essential for grasping elemental characteristics, predicting chemical reactions, and comprehending the formation of compounds.

Exploring Transition Metals

Transition metals are elements found in the d-block of the periodic table. They are unique because they can exhibit a wide range of oxidation states. Unlike other elements, transition metals have partially filled d-orbitals, allowing them to form compounds with various oxidation numbers.
These elements are not only central to the formation of different compounds but also are essential in many industrial applications. From catalysis to the formation of alloys, transition metals like iron, copper, and titanium are fundamental in both nature and technology.
Their ability to easily change oxidation states makes them particularly versatile in chemical reactions, significantly impacting everything from biology to material science.

Hydrogen: The Simplest Element

Hydrogen, the lightest and most abundant element in the universe, plays a crucial role in chemistry. It typically has an oxidation number of +1 when forming compounds but can also take on other forms, such as -1 in hydrides.
In most compounds, hydrogen's oxidation number of +1 is due to its single electron configuration that seeks to pair with other atoms. This feature allows it to bond with a wide array of elements, including sulfur. In compounds like hydrogen sulfide (H₂S), hydrogen's presence is marked by its consistent oxidation state that complements sulfur's -2 oxidation number.
From forming basic compounds like water (H₂O) to its role in organic chemistry, hydrogen is an indispensable element in both basic research and practical applications.

The Role of Oxygen in Compounds

Oxygen is a highly reactive element, most often displaying an oxidation number of -2 in compounds. This is primarily due to its high electronegativity, allowing it to attract electrons strongly.
Oxygen's interaction with sulfur is crucial in compounds such as sulfur dioxide (SO₂) or sulfuric acid (H₂SO₄). Here, the oxidation number of sulfur varies, but oxygen maintains its -2 state, acting as a strong oxidizing agent.
Beyond its role in simple compounds, oxygen is essential for life, being a part of the respiration process and participating in combustion reactions. Its ability to form stable bonds with many elements makes it indispensable in both inorganic and organic chemistry.