Chemical Bonding

🔹 1. What is Chemical Bonding?

Chemical bonding is the process by which atoms join together to form molecules or compounds by gaining, losing, or sharing electrons to achieve a stable electronic configuration (usually a full outer shell, like noble gases).

🔹 2. Types of Chemical Bonds

➤ 2.1 Ionic Bonding

Occurs when electrons are transferred from one atom to another.

• Typically occurs between metals (which lose electrons) and non-metals (which gain electrons).
• The atoms become ions (charged particles) and are held together by electrostatic attraction.

✅ Example:

Sodium chloride (NaCl)

• Sodium (Na) loses 1 electron → Na⁺
• Chlorine (Cl) gains 1 electron → Cl⁻
• Na⁺ and Cl⁻ are attracted to form NaCl.

Electron Configuration:

• Na: 2,8,1 → Na⁺: 2,8
• Cl: 2,8,7 → Cl⁻: 2,8,8

➤ 2.2 Covalent Bonding

Occurs when atoms share electrons to achieve full outer shells.

• Common between non-metal atoms.
• A shared pair of electrons forms the bond.

✅ Example:

Water (H₂O)

• Oxygen shares 2 of its electrons (one with each hydrogen).
• Each hydrogen shares 1 electron with oxygen.

Oxygen has 6 valence electrons → needs 2 more → shares 2 electrons
Hydrogen has 1 valence electron → needs 1 → shares 1 with oxygen

➤ 2.3 Metallic Bonding

Occurs in metals where atoms form a giant lattice of positive ions in a sea of delocalized electrons.

• The free-moving electrons allow metals to conduct electricity.
• The strong attraction between metal cations and delocalized electrons gives high melting and boiling points.

✅ Example:

Magnesium (Mg)

• Mg atoms release electrons to form Mg²⁺ ions.
• Electrons move freely throughout the metal structure.

🔹 3. Properties of Compounds by Bond Type

🔹 4. Dot and Cross Diagrams

✅ Example: Magnesium Oxide (MgO) — Ionic

• Mg: 2,8,2 → loses 2 electrons → Mg²⁺
• O: 2,6 → gains 2 electrons → O²⁻

✅ Example: Ammonia (NH₃) — Covalent

• N shares 3 electrons with 3 H atoms

🔹 5. Special Cases in Covalent Bonding

➤ Double and Triple Bonds

Some atoms need to share more than one pair of electrons.

✅ Example: Oxygen (O₂)

• Each O shares 2 electrons → double bond

✅ Example: Nitrogen (N₂)

• Each N shares 3 electrons → triple bond

🔹 6. Giant Covalent Structures

• Atoms connected by covalent bonds in a large 3D network.
• High melting and boiling points, hard, usually non-conductive.

✅ Examples:

• Diamond: Each carbon bonds with 4 others → very hard
• Graphite: Each carbon bonds with 3 others → soft, conducts electricity due to delocalized electrons
• Silicon dioxide (SiO₂): Network of Si and O atoms

🔹 7. Summary Table of Bonding Types

📌 Exam Tips

• Use dot and cross diagrams for both ionic and covalent bonds.
• Always state electron configurations for ionic bonds.
• Describe properties using particle structure (e.g., giant lattice, delocalized electrons).
• Know the differences between simple molecular, giant covalent, and metallic structures.

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