3.2 Properties of Solids

How many basic types of solids are there?

4

The 4 basic types of solids are:

Ionic solids, covalent network solids, molecular solids, metallic solids

Solids are classified by:

what type of component occupies the lattice points

A 3-dimensional system of points designating the positions of the centers of the components of a solid (atoms, ions, or molecules).

Lattice

Many properties of liquids and solids are determined by:

The strengths and types of intermolecular forces present

Ionic solids have ions at:

Points of the lattice that describes the structure of the solid.

Vapor pressure, melting point, and boiling point of ionic solids:

Low, high, high

Why do ionic solids have low vapor pressure, high melting point, and high boiling point?

Due to strong interactions between ions

The attraction between the positive and negative ion

Electrostatic attraction

Electrostatic attraction can be described by:

Coulomb’s law

How does Coulomb’s law describe electrostatic attraction?

It states that smaller ions &/or ions with higher charges will have stronger attractions between the ions resulting in higher lattice energy values.

Are ionic solids brittle?

Yes

Why are ionic solids brittle?

Due to the repulsion of like charges

When do ionic solids have repulsion of like charges?

When one layer slides across another layer

Can ionic solids conduct electricity?

Yes

When can ionic solids conduct electricity?

When the ions are mobile

When do ionic solids become mobile ions?

When it is melted (molten) or dissolved in water or another solvent.

Ionic solids are generally between:

Metal cation and non-metal anion

Are there non-metal cations?

Yes

Covalent network solids have atoms at the:

Lattice points

What type of points do covalent network solids have?

Strong directional covalent bonds

Covalent network solids might best be viewed as a:

“giant molecule”

Covalent network solids are only formed from:

Nonmetals

Different types of arrangements of covalent network solids:

Elemental or binary compounds of two nonmetals

Examples of elemental covalent network solid:

Diamond, graphite

Examples of binary compounds of two nonmetals for covalent network solids:

Silicon dioxide and silicon carbide

What type of atom is seen at lattice points in diamond and graphite?

Carbon

Examples of metalloids that bond to nonmetals to form covalent network solids:

B and Ge

How to melt covalent network solids?

Break covalent bonds

Covalent network solids are characterized by:

Hardness, strength, and high melting points

Why are covalent network solids typically characterized by hardness, strength, and high melting points?

Covalent bonds are relatively strong

Are three-dimensional network solids rigid and hard (brittle)?

Yes

Why are three-dimensional network solids rigid and hard (brittle)?

Covalent bond angles are fixed

Basis for biological compounds:

Carbon

How do carbon atoms arrange into diamond?

Form tetrahedral shaped covalent bonds which form a three-dimensional network

Characteristics of diamond:

Hard, basically colorless, insulator, high melting point

How do carbon atoms arrange into graphite?

Form two-dimensional networks which consist of layers

Bonds within each layer in graphite:

Strong covalent bonds

Bonds between each layer in graphite:

Weak London dispersion forces

Job of weak London dispersion forces in graphite:

Hold layers together

Characteristics of graphite:

Slippery, black, a conductor (within the plane), soft, high melting point

Why is graphite soft?

Adjacent layers can slide past each other relatively easily when the LDFs are broken

Basis for geological molecules:

Silicon

Examples of silicon-containing covalent network solids:

Silica (SiO2), glass, silicon carbide (SiC)

SiO2 consists of:

Many of SiO4 molecules in tetrahedral shape

Glass consists of an:

Amorphous solid

Solid with considerable disorder among components

Amorphous solid

When is glass produced?

When SiO2 is heated

The only chemical compound of carbon and silicon:

Silicon carbide (SiC)

Silicon carbide is an excellent:

Abrasive

Function of silicon carbide:

Make sand paper

Molecular solids are composed of:

Distinct, individual units of covalently-bonded molecules

Covalently-bonded molecules that make up molecular solids are attracted to each other through:

Relatively weak intermolecular forces

What is present at lattice points of molecular solids?

Molecules

Molecules used to form molecular solids are composed of:

Nonmetal atoms

The nonmetal atoms that the molecules used to form molecular solids are composed of are bonded by:

Covalent bonds

Boiling point of molecular solids:

Low

Why is boiling point of molecular solids low?

Intermolecular forces between the molecules are relatively weak

Do molecular solids conduct electricity?

No

Why don’t molecular solids conduct electricity?

Their valence electrons are tightly held within the covalent bonds and the lone pairs of each constituent molecule.

Molecular solids are sometimes composed of:

Very large molecules or polymers

Example of Molecular solid held together w/hydrogen bonds:

Ice (H2O)

Examples of Molecular solid held together with LDFs:

Dry ice (CO2), iodine (I2), sulfur (S8), phosphorous (P4), hydrocarbons (CxHy), polymers

Metallic solids consist of:

Metallic crystals with spherical metal atoms packed together and bonded to each other equally in all directions

A close packed lattice of positive atoms/ions surrounded by a sea of moving electrons

Metallic bond

Are metals good conductors of heat and electricity?

Yes

Why are metals good conductors of heat and electricity?

Movement of electrons

Are metals malleable and ductile?

Yes

Why are metals malleable and ductile?

Close packed atoms/ions allow for ease of rearranging of their structure

Metals alloys are:

Mixture of metals

Do alloys conduct?

Yes

Why do alloys conduct?

Keep a “sea” of electrons

Some alloys form a ______ on the surface

Chemically inert oxide layer

Example of alloy that forms a chemically inert oxide layer on the surface:

Stainless steel

Two main types of alloys:

Substitutional and interstitial

How do substitutional alloys form?

An atom of similar size substitutes for another atom in lattice

What is the density of a substitutional alloy?

Between the density values of the two metals

Why is the density of a substitutional alloy between the density values of the two metals?

They have similar radii

Do substitutional alloys remain malleable and ductile?

Yes

Example of substitutional alloy:

14k gold

14k gold is formed when:

Ag atoms replace some of the Au atoms

Interstitial alloy forms when:

A smaller atom fills the space between larger atoms

Do interstitial alloys remain the same malleability and ductility?

No

Why do interstitial alloys not remain the same malleability and ductility?

The lattice is more rigid

Why do interstitial alloys have a more rigid lattice?

The atoms have different radii

Example of interstitial alloy:

Steel

Structure of steel:

Carbon atoms fit between iron atoms

Where may noncovalent interactions occur in large biomolecules or polymers?

Between different molecules or between different regions of the same large biomolecule.

The functionality and properties of biomolecules and polymers depend strongly on:

The shape of the molecule

The shape of biomolecules and polymers is largely dictated by:

Noncovalent interactions

What happens when two parts of the same strand in a protein are attracted through hydrogen-bonding?

Forms secondary structure of biomolecule and gives it folded shape

What types of intramolecular forces give DNA molecules their structure?

Hydrogen-bonding between two parts of the same strand

Interaction of ionic solids:

Ionic

Properties of ionic solids:

High melting point, brittle, hard

Examples of ionic solids:

NaCl, MgO

Interaction(s) of molecular solids:

Hydrogen-bonding, dipole-dipole, London Dispersion

Properties of molecular solids:

Low melting points, non-conducting

Examples of molecular solids:

H2, CO2

Interaction of metallic solids:

Metallic bonding

Properties of metallic solids:

Variable hardness and melting point, conducting