Module 6: Formation of Ions and Compounds

Module 6 of Suharshi’s Basic Chemistry Course:

📘 Module 6: Formation of Ions and Compounds

🧠 Learning Objectives:

• Understand what ions are

• Differentiate between cations and anions

• Learn why atoms form ions (gain or lose electrons)

• Understand with examples how elements like Sodium and Chlorine form ions

• Visualize electron transfer in ionic bonding

🔹 What is an Ion?

An ion is a charged particle formed when an atom gains or loses one or more electrons.

• If an atom loses electrons, it becomes positively charged → Called a Cation.

• If an atom gains electrons, it becomes negatively charged → Called an Anion.

Important: Only electrons are gained or lost—protons in the nucleus remain unchanged.

🔹 Why Do Atoms Form Ions?

Atoms want to achieve a stable electron arrangement like that of noble gases (e.g., helium, neon, argon), which have a full outer shell.

• Metals (e.g., Sodium, Magnesium) tend to lose electrons to achieve stability.

• Non-metals (e.g., Chlorine, Oxygen) tend to gain electrons to complete their outer shell.

🟠 Example 1: How Sodium Becomes a Sodium Ion (Na⁺)

Atomic number of Sodium (Na) = 11
Electronic configuration: 2, 8, 1

Sodium has 1 electron in its outer shell. It loses that one electron to become stable:

Na → Na⁺ + e⁻
(Here, Na⁺ has 11 protons and only 10 electrons. Hence, it's a positively charged ion.)

🔵 Example 2: How Chlorine Becomes Chloride (Cl⁻)

Atomic number of Chlorine (Cl) = 17
Electronic configuration: 2, 8, 7

Chlorine needs 1 electron to complete its outer shell of 8. It gains 1 electron:

Cl + e⁻ → Cl⁻
(Cl⁻ has 17 protons and 18 electrons, making it negatively charged.)

🧲 Ionic Bonding: How Ions Combine to Form Compounds

When a metal and a non-metal react:

• Metal loses electrons → becomes cation

• Non-metal gains electrons → becomes anion

These oppositely charged ions attract each other to form an ionic bond.

🧂 Example: Sodium Chloride (NaCl)

Na → Na⁺ + e⁻
Cl + e⁻ → Cl⁻

Now Na⁺ and Cl⁻ are oppositely charged and combine to form NaCl (common salt).

📝 Summary:

• Ions are atoms with a charge.

• Cations are positive (lost electrons); anions are negative (gained electrons).

• Ions form so atoms can achieve a full outer shell.

• Ionic compounds like NaCl are formed when metal cations and non-metal anions bond.

📊 Activity: Electron Transfer Diagrams

Draw a diagram showing:

1. Sodium atom losing 1 electron → Na⁺

2. Chlorine atom gaining 1 electron → Cl⁻

3. Show how these form an ionic bond in NaCl