Ionic Crystals & Metals (College Board AP® Chemistry): Flashcards
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- FrontIonic Crystals
Define ionic crystal.
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Cards in this collection (24)
Define ionic crystal.
An ionic crystal is a solid in which positive and negative ions are arranged in a regular, three-dimensional lattice held together by strong Coulombic forces of attraction.
True or False?
The overall charge of an ionic lattice is neutral.
True.
Although an ionic lattice contains both cations and anions, the charges balance exactly so the overall structure carries no net charge.
The three-dimensional arrangement of ions in an ionic crystal maximizes Coulombic forces of .......... and minimizes forces of repulsion between equally charged ions.
The three-dimensional arrangement of ions in an ionic crystal maximizes Coulombic forces of attraction and minimizes forces of repulsion between equally charged ions.
Why are ionic crystals brittle rather than malleable?
When stress is applied, layers of ions shift relative to each other. This brings ions of the same charge into alignment, creating strong repulsive forces between like-charged ions that cause the crystal to fracture — splitting the lattice apart.
True or False?
Increasing the charge on the ions in an ionic compound decreases the Coulombic force of attraction.
False.
According to Coulomb's law, force is proportional to the product of the charges (q1 × q2). Increasing ionic charge increases the attractive force, resulting in a stronger lattice with higher melting point.
Why does ionic radius affect the strength of attraction in an ionic crystal lattice?
Coulombic force is inversely proportional to the square of the distance between charges (F ∝ 1/r²). Smaller ions place their charges closer together, increasing the attractive force and producing a stronger, higher-melting lattice.
Ionic compounds conduct electricity only when .......... or dissolved in solution, because ions must be free to move.
Ionic compounds conduct electricity only when molten or dissolved in solution, because ions must be free to move.
Define sea of electrons (metallic bonding).
The sea of electrons is the pool of delocalized valence electrons that move freely throughout a metallic lattice, surrounding the fixed metal cations and holding the structure together.
True or False?
Metals are malleable because the delocalized electrons allow layers of metal cations to slide past each other without breaking the bonding.
True.
The non-directional sea of electrons maintains cohesion even when cation layers shift position, which is why metals can be bent and shaped without fracturing.
Most metals have high melting points because of the strong .......... forces between metal cations and the sea of delocalized electrons.
Most metals have high melting points because of the strong electrostatic forces between metal cations and the sea of delocalized electrons.
How does metallic bonding explain why metals conduct both electricity and heat?
The delocalized electrons move freely throughout the lattice, carrying electrical charge when a voltage is applied and transferring kinetic energy rapidly when heat is applied. This freedom of movement accounts for both high electrical and thermal conductivity.
True or False?
Network covalent solids and metals both have high melting points, but only metals are good electrical conductors.
True.
Both structure types have strong bonding that requires significant energy to break. However, network covalent solids (except graphite) lack free-moving charged particles, so they do not conduct electricity as metals do.
In a diagram of metallic bonding, what do the positive signs and the surrounding dots typically represent?
The positive signs represent the metal cations fixed in the lattice (atoms that have lost their valence electrons). The surrounding dots represent the delocalized electrons — the sea of electrons — that move freely between and around the cations.
Define interstitial alloy.
An interstitial alloy is an alloy composed of atoms with vastly different radii, where the smaller atoms occupy the interstices (gaps) between the larger atoms arranged in a lattice.
Steel is an example of an interstitial alloy composed of .......... and carbon.
Steel is an example of an interstitial alloy composed of iron and carbon.
True or False?
In an interstitial alloy, both types of atoms must have similar atomic radii.
False.
Interstitial alloys are specifically formed from atoms with vastly different radii — the smaller atoms fit into the spaces between the larger lattice atoms. Similar radii characterise substitutional alloys.
Why do alloys often have different properties than the pure metals they contain?
Introducing atoms of a different element (whether into interstitial spaces or as substitutes) disrupts the regularity of the metal lattice. This makes it harder for lattice layers to slide past one another, which typically increases hardness and strength compared to the pure metal.
True or False?
Alloys containing elements from the first two periods of the periodic table are typically interstitial alloys.
True.
First- and second-period elements (such as carbon, hydrogen and nitrogen) have very small atomic radii, allowing them to fit into the interstices of a larger metal lattice.
An alloy is a homogeneous mixture formed when metals are melted, physically mixed, and .......... together.
An alloy is a homogeneous mixture formed when metals are melted, physically mixed, and cooled together.
Define substitutional alloy.
A substitutional alloy is an alloy in which atoms of the substituting element have similar radii to the original metal, allowing them to replace (substitute for) some of the host atoms in the lattice.
Brass is an example of a substitutional alloy composed of copper and .......... .
Brass is an example of a substitutional alloy composed of copper and zinc.
True or False?
In a substitutional alloy, the substituting atoms occupy the gaps between the host metal atoms.
False.
In a substitutional alloy, the substituting atoms replace host atoms at regular lattice positions. It is interstitial alloys in which smaller atoms occupy the gaps between larger host atoms.
What structural requirement must be met for a substitutional alloy to form?
The atoms of the substituting element must have a similar atomic radius to the atoms of the host metal. This allows them to occupy lattice sites without significantly distorting the overall lattice structure.
True or False?
Both interstitial and substitutional alloys are types of homogeneous mixtures.
True.
Both alloy types are formed by mixing metals (and sometimes nonmetals) in the liquid state and cooling them to produce a uniform solid solution — a homogeneous mixture throughout.
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