---
title: "Short note: metallic bond"
subject: "Civil Engineering Materials"
chapter: 1
key: "semester_3/civil_engineering_materials:metallic-bond-short-note"
source: https://www.bctengineer.com/q/semester_3/civil_engineering_materials/metallic-bond-short-note
site: BCT Engineering
---

# Short note: metallic bond

Civil Engineering Materials · Chapter 1: Introduction to Civil Engineering Material

- Asked in: 2066 Shrawan (old course), 4 marks
- Video: [Metals & Ceramics: Crash Course Engineering #19](https://www.youtube.com/watch?v=NOK1nMiiTWU) — CrashCourse
- Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14
- Page: https://www.bctengineer.com/q/semester_3/civil_engineering_materials/metallic-bond-short-note
- Whole chapter: https://www.bctengineer.com/md/semester_3/civil_engineering_materials/chapter-1

## Question

Write a short note on metallic bond.

## Short answer

Metallic bond is the electrostatic attraction between positive metal ions arranged in a lattice and a freely moving cloud of valence electrons. This non‑directional bond gives metals high electrical and thermal conductivity, ductility, malleability, and metallic luster; examples include iron, copper and aluminium.

## Answer

A **metallic bond** is the bond formed in metals, in which the outer (valence) electrons leave their atoms and move freely throughout the whole lattice. The metal consists of positive ions arranged in a regular lattice, held together by the electrostatic attraction of this "sea" of free electrons.

```text
  + . + . + . +      + = metal ion
  . + . + . + .      . = free electron
  + . + . + . +  (electrons move through the lattice)
```

#### Properties that result
- **High electrical and thermal conductivity**, because free electrons carry charge and heat.
- **Ductility and malleability:** layers of ions can slide over each other without breaking the bond, because the electron cloud is non-directional.
- **Metallic lustre** and opacity.
- **Moderate to high strength and melting point**, which increase with the number of free electrons (iron vs sodium).

Examples: iron, copper, aluminium, zinc and their alloys.

## Check yourself

The answer's key points as multiple-choice questions, with the correct option and why.

1. A metallic bond holds
   A. atoms by shared pairs
   B. positive ions in a lattice by a sea of free electrons
   C. ions by transfer
   D. molecules by hydrogen
   Answer: B. Definition. (Key point: Structure)

2. Metals are ductile because
   A. bonds are directional
   B. electrons are fixed
   C. layers of ions slide while the non-directional electron cloud holds them
   D. ions repel
   Answer: C. No bond breaking. (Key point: Ductility)

3. High conductivity arises from
   A. fixed ions
   B. directional bonds
   C. voids
   D. free electrons carrying charge and heat
   Answer: D. Stated. (Key point: Conductivity)

## Related in Civil Engineering Materials

- [Metallic bond versus covalent bond](https://www.bctengineer.com/question.md?key=semester_3%2Fcivil_engineering_materials%3Ametallic-covalent-bond) — Civil Engineering Materials, chapter 1