The Difference Between Ionic and Covalent Bonds
Dec 15
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When atoms combine, they form chemical bonds that hold them together. The two main types of bonding you’ll study in Unit 1 are ionic and covalent bonds. Understanding the difference helps explain why substances have different properties — from the salt on your chips to the water in your glass.
Ionic Bonding
An ionic bond forms when electrons are transferred from one atom to another. This usually happens between a metal and a non-metal.
Metals lose electrons, forming positive ions (cations).
Non-metals gain electrons, forming negative ions (anions).
The oppositely charged ions attract each other through strong electrostatic forces.
Example: Sodium (Na) donates one electron to chlorine (Cl) → Na⁺ and Cl⁻ form sodium chloride (NaCl).These strong ionic bonds create giant lattices with high melting points.
Covalent Bonding
A covalent bond forms when two non-metal atoms share electrons to achieve a full outer shell. The shared pair of electrons attracts both nuclei, holding the atoms together.
Example: In water (H₂O), each hydrogen shares one electron with oxygen, creating two covalent bonds.
Covalent substances can form:
Simple molecules (like CO₂ and H₂O) — low melting/boiling points, no free ions, poor conductors.
Giant covalent structures (like diamond or graphite) — very strong, high melting points.
Summary Table
Property | Ionic Bonding | Covalent Bonding |
Type of atoms | Metal + Non-metal | Non-metal + Non-metal |
Electron movement | Transferred | Shared |
Structure | Giant lattice | Simple molecules or giant network |
Melting point | High | Low (except diamond/graphite) |
Conductivity | Conducts when molten or dissolved | Usually poor conductor |
Exam Tip
“Ionic bonds involve electron transfer forming charged ions held by electrostatic attraction, while covalent bonds involve shared electron pairs between non-metals.”
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