Question

Assign oxidation states to all of the atoms in each of the following ions. a. \(\mathrm{NH}_{4}^{+}\) b. \(\mathrm{HCO}_{3}^{-}\) c. \(\mathrm{OH}^{-}\) d. \(\mathrm{Cr}_{2} \mathrm{O}_{7}^{2-}\)

Short answer

The short answer for the oxidation states of each atom in the given ions is: a. \(NH_{4}^{+}\): N = -3, H = +1 b. \(HCO_{3}^{-}\): H = +1, C = +4, O = -2 c. \(OH^{-}\): O = -2, H = +1 d. \(Cr_{2}O_{7}^{2-}\): Cr = +6, O = -2

Step-by-step solution

For ion \(\mathrm{NH}_{4}^{+}\)

1. The oxidation state of hydrogen in a compound is usually +1. 2. Nitrogen's oxidation state is unknown (let's denote it as x). 3. The overall charge of the ion is +1. 4. Set up an equation: x + 4(+1) = +1. 5. Solve for x to obtain the oxidation state of nitrogen: x = -3. So, the oxidation states of atoms in \(\mathrm{NH}_{4}^{+}\) are: N = -3, H = +1.

For ion \(\mathrm{HCO}_{3}^{-}\)

1. The oxidation state of hydrogen in a compound is usually +1. 2. Carbon's oxidation state is unknown (let it be x). 3. The oxidation state of oxygen in a compound is usually -2. 4. The overall charge of the ion is -1. 5. Set up an equation: (+1) + x + 3(-2) = -1. 6. Solve for x to obtain the oxidation state of carbon: x = +4. So, the oxidation states of atoms in \(\mathrm{HCO}_{3}^{-}\) are: H = +1, C = +4, O = -2.

For ion \(\mathrm{OH}^{-}\)

1. The oxidation state of oxygen in a compound is usually -2. 2. The oxidation state of hydrogen in a compound is usually +1. 3. The overall charge of the ion is -1. 4. Since the total charge should be equal to the overall charge: (-2) + (+1) = -1. The oxidation states of atoms in \(\mathrm{OH}^{-}\) are: O = -2, H = +1.

For ion \(\mathrm{Cr}_{2}\mathrm{O}_{7}^{2-}\)

1. The oxidation state of oxygen in a compound is usually -2. 2. Chromium's oxidation state is unknown (let it be x). 3. Since there are two chromium atoms, the total oxidation state due to chromium will be 2x. 4. The overall charge of the ion is -2. 5. Set up an equation: 2x + 7(-2) = -2. 6. Solve for x to obtain the oxidation state of chromium: x = +6. So, the oxidation states of atoms in \(\mathrm{Cr}_{2}\mathrm{O}_{7}^{2-}\) are: Cr = +6, O = -2.

Key concepts

Ions and Their Charges

Ions are essential components in chemistry, often formed when atoms gain or lose electrons. This loss or gain results in an atom having a net electric charge, turning it into an ion. For example, when a neutral hydrogen atom loses an electron, it becomes a positively charged ion (H⁺). Conversely, a chlorine atom gains an electron to form a negatively charged ion (Cl⁻). These charges are crucial because they dictate how ions interact in chemical reactions.
Understanding ions involves:

• Recognizing that positive ions are called cations.
• Understanding negative ions are known as anions.
• Knowing that opposite charges attract, leading to the formation of chemical compounds.

Familiarity with ions is a stepping stone to mastering more complex topics like chemical bonding and reactions.

Chemical Compounds and Their Formation

Chemical compounds are substances formed when atoms of different elements bond together in fixed proportions. The formation of these compounds involves ionic or covalent bonding, determined by how electrons are shared or transferred between atoms. For instance, in the ionic compound sodium chloride (NaCl), sodium loses an electron, and chlorine gains one, resulting in oppositely charged ions that attract each other.
Key points on chemical compounds include:

• Comprehending the basic types of bonding: ionic, covalent, and metallic.
• Recognizing that compounds have properties different from the elements they consist of.
• Identifying chemical formulas that provide insight into the element proportions in a compound.

Understanding chemical compounds forms the basis for exploring chemical reactions and their applications in real-world scenarios.

Oxidation and Its Significance

Oxidation is a crucial concept in chemistry, relating to the loss of electrons by an atom or ion. It often occurs in tandem with reduction, where another species gains the electrons lost. This process is pivotal in numerous chemical reactions, including those vital for life, such as cellular respiration and photosynthesis.
Points to remember about oxidation include:

• Oxidation states, which help track electron transfers in reactions.
• The principle that oxidation involves an increase in oxidation state.
• Understanding oxidation as part of redox reactions, where oxidation and reduction happen simultaneously.

Grasping oxidation deeply enhances comprehension of energy changes and reaction mechanisms.

Chemistry Education and Understanding Concepts

Chemistry education aims to build a robust understanding of both fundamental and complex chemical concepts, making it accessible for learners. This involves breaking down intricate ideas like ions, oxidation, and chemical compounds into easy-to-digest segments. Using various educational techniques, such as guided problem-solving and real-world examples, supports learners in grasping concepts effectively.
Strategies in chemistry education include:

• Utilizing visual aids to illustrate complex processes.
• Employing analogies to relate abstract concepts to everyday experiences.
• Encouraging hands-on experiments to reinforce theoretical learning with practical experience.

Effective chemistry education empowers students to connect theoretical knowledge with practical applications, fostering a deeper appreciation and understanding of the natural world.