Metallic Bonding — Practice · Grade 11 Science

Chapter: Bonding, Formulas & Molecular Structure

What this practice covers

By the end of Metallic Bonding you should be able to:

10 questions, multiple choice and written answer, each with a worked explanation.

Vocabulary used: metallic bond, delocalized electrons, electron sea, malleable, ductile, luster, alloy.

Problem 1

In the electron-sea model, metal atoms are best described as…
  1. separate molecules sharing electron pairs
  2. neutral atoms locked rigidly in place
  3. positive ions surrounded by mobile, delocalized electrons
  4. negative ions in a fixed lattice
Answer and explanation

positive ions surrounded by mobile, delocalized electrons

Metals form positive ions that sit in a shared sea of freely moving delocalized electrons.

Problem 2

Which property of metals is most directly explained by their delocalized (free-moving) electrons?
  1. low density
  2. transparency
  3. brittleness
  4. electrical conductivity
Answer and explanation

electrical conductivity

Free-moving electrons can drift under a voltage, carrying an electric current, so metals conduct electricity.

Problem 3

Why are metals malleable (able to be hammered into sheets)?
  1. Their ions can slide past one another while the electron sea keeps holding them together
  2. Their bonds are rigid and point in fixed directions
  3. They contain no electrons to get in the way
  4. They are made of separate small molecules
Answer and explanation

Their ions can slide past one another while the electron sea keeps holding them together

When struck, layers of metal ions shift, but the mobile electron sea flows with them and keeps the metal bonded, so it bends instead of breaking.

Problem 4

Explain how metallic bonding is different from ionic bonding.
Answer and explanation

In ionic bonding, electrons are fully transferred from a metal to a nonmetal, creating positive and negative ions locked in a rigid lattice. In metallic bonding, the metal atoms' valence electrons are not transferred to any single atom but are shared among all of them in a mobile 'sea,' so the electrons stay free to move and the bond reaches in every direction.

Problem 5

The shiny luster of a polished metal surface is explained by…
  1. its rigid ionic lattice
  2. the free electrons absorbing and re-emitting light
  3. the metal's very high density
  4. electrons that are tightly bound to each atom
Answer and explanation

the free electrons absorbing and re-emitting light

The delocalized electrons readily absorb light and re-emit it, reflecting it back to give a shiny surface.

Problem 6

A salt (ionic) crystal shatters when struck, but a copper bar just bends. What is the best explanation?
  1. Salt is much softer than copper
  2. Copper is actually a gas at room temperature
  3. Copper's electron sea lets layers of ions shift while staying bonded, but shifting an ionic lattice aligns like charges that repel and split it
  4. Copper contains no chemical bonds at all
Answer and explanation

Copper's electron sea lets layers of ions shift while staying bonded, but shifting an ionic lattice aligns like charges that repel and split it

The mobile electron sea holds shifting metal ions together, while in an ionic solid a shifted layer brings like charges together, and they repel and cleave the crystal.

Problem 7

Why does a metal usually conduct better than a solid ionic crystal? Show the reasoning, not just the conclusion.
Hints

A model explains trends, but real alloys and structures affect behavior.

Answer and explanation

It has mobile delocalized electrons; ordinary ionic solids lack comparably mobile ions.

Problem 8

Can all metals be assumed to have identical strength because bonding is metallic?
Hints

State what the supplied observations or conditions establish, and separate that from any assumption.

Answer and explanation

No. Composition, crystal structure, defects and processing affect mechanical properties.

Problem 9

An alloy changes a material’s composition and internal arrangementAn alloy changes a material’s composition and internal arrangementSubstitutional exampleInterstitial exampleAlloy composition and microstructure can alter deformation.AAAAAAAABAAAAAAAAA
Original topology comparison; atom sizes, spacing and alloy concentrations are illustrative rather than a specific crystal structure.
Interpret the supplied visual. What distinguishes the two selected alloy models?
Answer and explanation

The substitutional species replaces a host-site occupant; the interstitial species occupies a space between host sites in the simplified arrangement.

An alloy combines a metallic element with one or more other elements. In a substitutional model, some host sites are occupied by another species; in an interstitial model, smaller atoms occupy spaces between selected host sites. Both can influence dislocation motion and properties. Real alloys may include several phases and complex microstructures, so a uniform dot pattern is not a universal atom-by-atom picture. State composition, treatment and measured property before recommending an alloy for a design.

The substitutional species replaces a host-site occupant; the interstitial species occupies a space between host sites in the simplified arrangement.

Response criteria

  • Interpret labels, structures, axes, units and directions correctly.
  • Explain the chemistry relationship or mechanism.
  • Respect stated assumptions and distinguish observation from inference.

Problem 10

A part requires strength index ≥60 and conduction index ≥70. Materials P, Q and R score (65,80), (90,50), and (50,95). Select a feasible option and name a missing design consideration.
Answer and explanation

P satisfies both stated constraints. Q fails conduction and R fails strength. Cost, corrosion, fatigue, fabrication or service temperature could still change the decision.

P satisfies both stated constraints. Q fails conduction and R fails strength. Cost, corrosion, fatigue, fabrication or service temperature could still change the decision.

Response criteria

  • Use the stated measurements or conditions, with correct units.
  • Connect the result to the chemical mechanism or evidence relationship.
  • Identify the assumption, model limit or further evidence requested.

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