How to Calculate Oxidation Numbers Introduction

Summary

This educational video script offers a detailed guide on determining oxidation numbers in chemical compounds. It outlines basic rules, such as elements in their pure form having an oxidation number of 0, and monatomic ions having an oxidation number equal to their ion charge. The script progresses to examples like KCl, MgO, CO, NH3, and NO2-, explaining how to apply these rules and the importance of the sum of oxidation numbers equaling zero in neutral compounds. It also covers exceptions, like halogens with oxygen, and ends with a teaser for more practice problems in a follow-up video.

Takeaways

• 📚 The video explains how to determine oxidation numbers for elements in a chemical compound.
• 🔢 An element by itself has an oxidation number of 0.
• ⚡ Monatomic ions have an oxidation number equal to their ion charge.
• 📐 The sum of oxidation numbers in a neutral compound equals 0.
• 📋 Group 1A elements (like potassium) have an oxidation number of +1.
• 🌀 Halogens usually have an oxidation number of -1, unless combined with oxygen.
• 💡 For compounds like CO, use the known oxidation number of oxygen (-2) to find the unknown (carbon in this case).
• 🌿 Hydrogen typically has a +1 oxidation number when combined with nonmetals.
• 🔄 For polyatomic ions, the sum of oxidation numbers equals the ion charge.
• 🧪 In challenging examples like BrO3-, halogens can have positive oxidation numbers when paired with oxygen.
• 📈 Practice is key to mastering the process of determining oxidation numbers.

Q & A

What is the oxidation number of an element by itself?

The oxidation number of an element by itself is always 0.

What is the oxidation number of monatomic ions?

The oxidation number of monatomic ions is the same as their ion charge.

How do you write oxidation numbers?

Oxidation numbers are written with the sign first (positive or negative) followed by the number.

What is the sum of oxidation numbers for a neutral compound?

The sum of oxidation numbers for a neutral compound equals 0.

What is the oxidation number of potassium (K) in the compound KCl?

The oxidation number of potassium (K) in KCl is +1.

What is the oxidation number of chlorine (Cl) in KCl?

The oxidation number of chlorine (Cl) in KCl is -1.

Why is the oxidation number of hydrogen in NH3 +1?

Hydrogen is +1 with nonmetals, and nitrogen is a nonmetal, so hydrogen in NH3 has an oxidation number of +1.

What is the oxidation number of nitrogen in NH3?

The oxidation number of nitrogen in NH3 is -3, calculated by the rule that the sum of oxidation numbers in a neutral compound must be 0.

How do you determine the oxidation number of carbon in CO?

The oxidation number of carbon in CO is +2, determined by the rule that the sum of oxidation numbers in a neutral compound must be 0, with oxygen being -2.

What is the oxidation number of calcium in CaC2?

The oxidation number of calcium in CaC2 is +2, calculated by the rule that the sum of oxidation numbers in a neutral compound must be 0, with each carbon being -1.

What is the oxidation number of nitrogen in NO2-?

The oxidation number of nitrogen in NO2- is +3, determined by the rule that the sum of oxidation numbers in a polyatomic ion equals the ion charge.

Why is the oxidation number of bromine in BrO3- not -1?

The oxidation number of bromine in BrO3- is +5, not -1, because it is paired with oxygen, which changes the typical oxidation number for halogens.

What is the oxidation number of chlorine in ClF3?

The oxidation number of chlorine in ClF3 is +3, determined by the rule that fluorine is always -1, and the sum of oxidation numbers in a neutral compound must be 0.