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AP Chemistry Practice Quiz: Structure of Metals and Alloys

Written by AP Content Team, Verified for 2026 AP Exams, Last updated: July 2026

Test your understanding with short quizzes. This quiz has 10 questions to check your progress.

Question 1 of 10

Which of the following best describes the 'sea of delocalized electrons' model used to represent metallic solids?

All Questions (10)

Which of the following best describes the 'sea of delocalized electrons' model used to represent metallic solids?

A) A model where valence electrons are free to move throughout the entire structure, not being bound to any single atom.

B) A model where electrons are transferred from a metal to a nonmetal, forming a rigid crystal lattice.

C) A model where atoms share electrons in localized bonds to form discrete molecules.

D) A model describing the weak attractive forces between oppositely charged ions in a solid.

Correct Answer: A

The provided content states that metallic bonding is represented as an array of positive metal ions within a 'sea of delocalized' valence electrons. This delocalization means the electrons are not associated with a single atom and are free to move.

In the model for a metallic solid, the structure is represented as an array of which two components?

A) Neutral metal atoms and shared electron pairs

B) Positive metal ions and delocalized valence electrons

C) Positive and negative ions in a fixed lattice

D) Metal atoms and interstitial nonmetal atoms

Correct Answer: B

The content explicitly defines the model of metallic bonding as 'an array of positive metal ions within a 'sea of delocalized' valence electrons.'

An alloy is formed by introducing small nitrogen atoms into the crystal lattice of larger titanium atoms. The nitrogen atoms occupy the spaces between the titanium atoms. What type of alloy is formed?

A) A substitutional alloy

B) An ionic compound

C) An interstitial alloy

D) A pure metallic solid

Correct Answer: C

According to the provided content, interstitial alloys form when smaller atoms fill the spaces between larger atoms. This scenario perfectly matches the definition.

Brass is an alloy of copper and zinc. Based on the provided information, why is brass classified as a substitutional alloy?

A) Because zinc atoms are much smaller than copper atoms and fill the gaps in the lattice.

B) Because zinc and copper atoms have comparable atomic radii, allowing one to replace the other in the lattice.

C) Because zinc transfers its valence electrons to the sea of electrons created by copper.

D) Because zinc and copper form a rigid ionic bond within the metallic structure.

Correct Answer: B

The content states that substitutional alloys form when 'atoms of comparable radius substitute for each other in the lattice' and uses brass as a specific example.

Element X has an atomic radius of 150 pm, and Element Y has an atomic radius of 75 pm. If an alloy is formed between these two elements, which type is it most likely to be, and why?

A) Substitutional, because the atoms have very different radii.

B) Interstitial, because the smaller Y atoms can fit into the spaces between the larger X atoms.

C) Substitutional, because the atoms have comparable radii.

D) Interstitial, because the larger X atoms can fit into the spaces between the smaller Y atoms.

Correct Answer: B

The significant difference in atomic radii (150 pm vs. 75 pm) indicates that the smaller atom (Y) will fit into the interstices (spaces) of the lattice formed by the larger atom (X). This is the definition of an interstitial alloy.

A student observes a two-dimensional model of a solid. The model shows a regular, repeating lattice of large, gray spheres. In several positions, a gray sphere has been replaced by a red sphere of a very similar size. What does this model most likely represent?

A) A pure metallic element

B) An interstitial alloy

C) A substitutional alloy

D) An ionic solid

Correct Answer: C

The model described shows atoms of comparable radius ('very similar size') substituting for each other in the lattice, which is the essential characteristic of a substitutional alloy.

What is the primary structural difference between an interstitial alloy and a substitutional alloy based on the provided definitions?

A) The type of bonding; one is metallic and the other is covalent.

B) The relative size of the component atoms and their subsequent position in the crystal lattice.

C) The number of delocalized electrons per atom.

D) The overall density of the resulting material.

Correct Answer: B

The provided content defines the two alloy types based on the relative atomic sizes and placement. Interstitial alloys involve small atoms in the spaces, while substitutional alloys involve atoms of comparable size replacing each other in the lattice.

Steel is a common alloy primarily composed of iron and carbon. According to the provided information, how is steel classified?

A) As a substitutional alloy, because carbon and iron atoms are similar in size.

B) As an interstitial alloy, because smaller carbon atoms fill spaces between larger iron atoms.

C) As a pure metal, because it is mostly iron.

D) As a substitutional alloy, because iron substitutes for carbon in the lattice.

Correct Answer: B

The content explicitly uses steel ('carbon in steel') as the example of an interstitial alloy, which forms when smaller atoms fill the spaces between larger atoms.

Given the following atomic radii: Gold (Au) = 144 pm, Silver (Ag) = 144 pm, Carbon (C) = 77 pm, and Iron (Fe) = 126 pm. Which pair of elements would most likely form a substitutional alloy?

A) Iron and Carbon

B) Gold and Carbon

C) Gold and Silver

D) Silver and Carbon

Correct Answer: C

Substitutional alloys form between atoms of 'comparable radius'. Comparing the radii, Gold (144 pm) and Silver (144 pm) have identical radii, making them ideal for forming a substitutional alloy. The pairs involving Carbon (77 pm) have significantly different radii and would form interstitial alloys.

Which of the following descriptions best represents a model of an interstitial alloy like steel?

A) A lattice of metal cations of comparable size randomly replacing one another, surrounded by a sea of electrons.

B) A lattice of large metal cations with much smaller atoms occupying the voids between them, all within a sea of electrons.

C) An array of positive and negative ions held together by electrostatic forces.

D) A regular lattice of uniform metal cations in a sea of delocalized valence electrons.

Correct Answer: B

This description accurately captures the two key features of an interstitial alloy model: a primary lattice of larger atoms (metal cations) and smaller atoms filling the spaces (voids), all held together by metallic bonding ('sea of electrons'). Option A describes a substitutional alloy, and Option D describes a pure metal.