Properties of Metallic Solids and Bonding

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Questions and Answers

Which of the following properties is NOT characteristic of metallic solids?

Malleability

High electrical conductivity

Brittleness (correct)

Luster

What does the 'sea of electrons' model in metallic bonding describe?

Electrons are fixed in place around metal atoms.

Metal atoms are loosely packed without any electron interaction.

Electrons are evenly distributed within a crystal lattice.

Electrons move freely around and between metal atoms. (correct)

In band theory, what happens as the number of metal atoms in a structure increases?

Malleability and ductility decrease significantly.

The available orbitals stack closely together in energy. (correct)

Available orbitals form a distinct gap.

Electrons become trapped in fixed positions.

Which of the following statements accurately describes thermal conductivity in metals?

High electrical conductivity in metals also indicates high thermal conductivity. Signup and view all the answers

What characteristic allows metals to be drawn into wires?

Ductility Signup and view all the answers

Which type of solid is characterized by the mutual attraction between cations and anions?

Ionic solids Signup and view all the answers

What is a primary characteristic of molecular solids?

They tend to be soft and have low melting points. Signup and view all the answers

Amorphous solids differ from crystalline solids in that they:

Lack an ordered internal structure. Signup and view all the answers

What holds covalent-network solids together?

Extended networks of covalent bonds Signup and view all the answers

What is a common property of metallic solids?

They exhibit malleability and ductility. Signup and view all the answers

Which characteristic is NOT typically associated with molecular solids?

High melting points Signup and view all the answers

Which type of solid is likely to be the hardest and most brittle?

Covalent-network solids Signup and view all the answers

Under normal laboratory conditions, most elements exist as which physical state?

Solids Signup and view all the answers

What is the electronic structure of graphene classified as?

Semimetal Signup and view all the answers

What is one of the main benefits of graphene's two-dimensional structure?

It enables electrons to travel long distances without scattering. Signup and view all the answers

In what type of applications is graphene's heat conductivity particularly advantageous?

Thermal management in microelectronics Signup and view all the answers

What characteristic of graphene makes it suitable for use in supercapacitors?

Its high surface-area-to-volume ratio Signup and view all the answers

What is an application of graphene in the field of electronics?

Next-generation flexible displays Signup and view all the answers

What challenge is associated with advancements in nanotechnology as exemplified by graphene?

High manufacturing costs Signup and view all the answers

What happens to an elastomer when the stretching or bending force is removed?

It regains its original shape. Signup and view all the answers

What is the first stage of addition polymerization?

Initiation Signup and view all the answers

How does graphene compare to copper in terms of electrical current densities?

It supports higher densities. Signup and view all the answers

Which property best describes rubber in the context of elastomers?

It can recover its shape after being distorted. Signup and view all the answers

Which application of graphene might benefit DNA sequencing?

Efficient sensors Signup and view all the answers

What distinguishes termination from the other stages of addition polymerization?

It stops the growth of the polymer chain. Signup and view all the answers

What does the variable 'n' indicate in the polymerization equation?

The number of monomer molecules reacting. Signup and view all the answers

What has contributed to the complexity of producing polyethylene?

The need for specific manufacturing conditions. Signup and view all the answers

Why is polyethylene considered an important material?

Its annual production exceeds 170 billion pounds. Signup and view all the answers

Which stage in addition polymerization follows initiation?

Propagation Signup and view all the answers

What is the degree of polymerization?

The average number of repeating units in a polymer Signup and view all the answers

What characterizes homopolymers?

They are formed from a single type of monomer Signup and view all the answers

What is a key feature of condensation polymerization?

Small molecules are produced during the reaction Signup and view all the answers

Why are polymers commonly used in engineering materials?

Their properties can be tailored through monomer selection Signup and view all the answers

What type of polymers are typically created through addition polymerization?

Homopolymers Signup and view all the answers

In chain termination, what happens to the polymer molecule?

It stops growing longer and produces a distribution of lengths Signup and view all the answers

Which reaction pair is involved in condensation polymerization?

An amine and a carboxylic acid Signup and view all the answers

What does the molecular mass distribution in polymers reflect?

The occurrence of termination steps during polymer growth Signup and view all the answers

Study Notes

Metallic Solids Properties

Possess a characteristic luster (shine) when their surface is clean.
Feel cold to the touch.
Exhibit high electrical conductivity, facilitating easy flow of electrically charged particles.
High electrical conductivity implies high thermal conductivity.
Are mostly malleable (hammered into thin sheets).
Are mostly ductile (drawn into wires).

Metallic Bonding Models

The "sea of electrons" model offers a basic qualitative explanation.
Band theory provides a more quantitative model, explained using the example of lithium atoms in a carbon nanotube. In a large number of atoms, available orbitals cluster closely in energy; the lower half is filled, forming the valence band.

Classification of Solids

Metallic solids: Held together by metallic bonds.
Ionic solids: Held together by the attraction between cations and anions; tend to be hard but brittle.
Covalent-network solids: Held together by an extended network of covalent bonds.
Molecular solids: Held together by weaker forces (dispersion forces, dipole-dipole interactions, hydrogen bonds); tend to be soft with low melting points.

Structure of Solids

Many solids have repeating three-dimensional patterns.
Amorphous solids lack ordered internal structure; particles are randomly arranged. Elastomers are an example, regaining shape after distortion unless past their elastic limit (rubber is a familiar example).

Polymer Creation: Addition Polymerization

Monomers couple through multiple bonds.
Initiation: Double bonds in monomers open, forming new bonds with other monomers.
Propagation: Each monomer adds to the chain.
Termination: Chain growth stops. Equation: n(monomer) → polymer (where n is a large number of monomers). Polyethylene is an example, with annual production exceeding 170 billion pounds.

Degree of Polymerization

Polymer chains vary in length due to random termination.
Degree of polymerization describes the average number of repeating units, usually calculated by mass.

Polymer Creation: Condensation Polymerization

Monomers have two functional groups that react, releasing a small molecule (e.g., water). Example: An amine (R-NH2) and a carboxylic acid (R-COOH) react to form a bond between N and C, releasing H2O.

Polymer Types

Homopolymers: Formed from a single type of monomer; contain one repeating unit; often made by addition polymerization.

Graphene

A two-dimensional form of carbon, isolated from graphite.
A semimetal with a zero energy gap.
Electrons travel long distances without scattering.
Can sustain high electrical current densities (six orders of magnitude higher than copper).

Graphene Applications

Thermal: Heat sinks and dissipation films in microelectronics and larger applications.
Energy storage: High surface area makes it suitable for batteries and supercapacitors.
Coatings, sensors, electronics: Anti-corrosion coatings, sensors, flexible displays, solar panels, etc.

Challenges in Nanotechnology

Innovations come with a cost (unspecified).

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Description

Explore the fascinating properties of metallic solids, including their characteristic luster and conductivity. Learn about different bonding models, notably the 'sea of electrons' and band theory. This quiz covers the classification of solids and the unique attributes of metallic bonds.