📖 Lesson 4: Ionic and Covalent Compounds

👩🏽‍🏫 Introduction

Hey future chemist! 👩🏽‍🔬👨🏽‍🔬

Have you ever wondered why salt dissolves in water but oil doesn’t? Or why diamonds are so strong while sugar melts easily? The answer lies in chemical bonds—the forces holding atoms together.

In this lesson, you’ll learn the two main types of chemical bonds: Ionic and Covalent. Understanding these will help you predict how substances behave—like whether they dissolve, conduct electricity, or have high melting points.

📘 Core Concepts

🔹 What is a Chemical Bond?

A chemical bond is a force that holds atoms together to form compounds. The two major types are:

1. Ionic bonds 🔗

2. Covalent bonds 🔗

🔹 Ionic Compounds

An ionic bond is formed when one atom transfers electrons to another atom. This usually happens between:

• Metals (which lose electrons)

• Non-metals (which gain electrons)

Example: Sodium Chloride (NaCl)

• Sodium (Na) loses 1 electron → becomes Na⁺

• Chlorine (Cl) gains 1 electron → becomes Cl⁻

• Opposite charges attract → forms NaCl

🧲 Ionic compounds are held together by electrostatic attraction between positive and negative ions.

🔹 Covalent Compounds

A covalent bond is formed when atoms share electrons. This usually happens between non-metals.

Example: Water (H₂O)

• Each hydrogen shares 1 electron with oxygen

• All atoms get full outer shells by sharing

🤝 Covalent bonding = sharing electrons to stay stable.

🧪 Comparing Ionic vs. Covalent Compounds

⚛️ Ionic Bond Formation (NaCl)

⚛️ Covalent Bond Formation (H₂O)

👩🏽‍🔬 Real-Life Examples

🧩 Sample Problem Walkthrough

🧠 Problem:

Identify the type of bond in the following compounds and justify your answer:
a) Carbon dioxide (CO₂)
b) Potassium bromide (KBr)

✅ Step-by-Step Solution:

• a) CO₂

  • Carbon and oxygen are both non-metals

  • They share electrons → Covalent bond

• b) KBr

  • Potassium = metal, Bromine = non-metal

  • Potassium gives an electron to bromine → Ionic bond

✔️ Final Answers:

• CO₂ → Covalent

• KBr → Ionic

✍🏽 Practice Exercises

Exercise 1: Fill-in-the-Blanks

1. In ionic bonding, electrons are ______.

2. In covalent bonding, atoms ______ electrons.

3. Ionic bonds usually form between a ______ and a ______.

Answers:

1. transferred

2. share

3. metal, non-metal

Exercise 2: Multiple Choice

1. Which of the following is a covalent compound?
   A. Sodium chloride
   B. Magnesium oxide
   C. Methane (CH₄)
   D. Calcium bromide

✅ Answer: C. Methane (CH₄)

2. Which compound will likely conduct electricity in water?
   A. Sugar (C₆H₁₂O₆)
   B. Salt (NaCl)
   C. Oxygen (O₂)
   D. Water (H₂O)

✅ Answer: B. Salt (NaCl)

Exercise 3: Match the Bond Type

Answers:

• HCl → Covalent

• NaCl → Ionic

• CO₂ → Covalent

• CaCl₂ → Ionic

🌀 Recap

Let’s summarize:

• Ionic compounds form through electron transfer (metal + non-metal), and are usually solid, with high melting points and good electrical conductivity in solution.

• Covalent compounds form through electron sharing (non-metal + non-metal), and are usually gases or liquids, with lower melting points and poor conductivity.

• The properties of compounds depend on the type of bond holding the atoms together.

💭 Reflection Prompt

Think about two things you used today—maybe salt, soap, water, or toothpaste. Try to classify them as ionic or covalent compounds. What clues helped you decide? Write your thoughts in your science journal.