CHE 202 chapter 12: structures of solids

crystalline solids

solids in which the particles are arrangeed in a highly ordered manner

amorphous solids

solids in which there is no particular order in the arrangement of particles

unit cell

smallest repeating unit in a crystal that reproduces the whole cryatal when it is stack repeatedly

crystal lattice

a framework used to represent crystalline solids as 3-D array of points in space

ionic solids (i.e salts)

consist of ions held together by ionic bonds and have a very high melting point.

molecular solids (i.e argon, methane, sucrose, dry ice, CO2)

atoms or molecules held together by intermolecular forces (dipole – dipole, London dispersion, hydrogen bonding). Have low to moderate melting points.)

covalent network

solids connected by a strong network of covalent bonds. Have very high melting points. E.g., sand (SiO2), diamond (carbon)

metallic solids

consist of entirely metallic atoms. Bonding is due to delocalized valence electrons

and the mobility of the electrons explains the good electrical conductivity of metals.

polymers

molecules of high molecular weight made by joining smaller molecules, called monomers

addition polymers

formed when a bond breaks, and the electrons in that bond make two new bonds.

condesation polymers

Are formed when a small molecule is removed between two large molecules

nanomatertials

Particles that have three dimensions on the 1–100 nm size

Which of the following statements is true about crystalline solids?

Crystalline solids have a repeating, highly ordered structure

What is the smallest repeating unit in a crystal lattice called?

unit cell

How many total atoms are present in a body-centered cubic (BCC) unit cell?

2 atoms per unit cell

Which of the following elements crystallizes in a face-centered cubic (FCC) structure?

aluminum

Which type of cubic unit cell has the highest packing efficiency?

Face-centered cubic (74%)

Which type of solid is held together only by intermolecular forces

molecular solid

Which of the following would have the highest melting point?

A) NaCl
B) H₂O
C) Ar
D) CO₂

NaCl

Why do metallic solids conduct electricity?

They have free-moving valence electrons.

What type of polymer is formed when a small molecule (like H₂O) is removed during polymerization?

Condensation polymer

Which of the following statements about nanomaterials is true?

They have different physical and chemical properties at the nanoscale.

Which of the following is an example of a molecular solid?
A) Diamond
B) NaCl
C) CO₂
D) Fe

CO₂

Which factor has the greatest effect on the strength of an ionic bond?

The size and charge of the ions

A material with a higher coordination number generally has:

higher density

A solid has a very high melting point, great hardness, and poor electrical conduction. This is a(n) __________ solid.

covalent network

Metallic solids do not exhibit __________.

extreme brittleness

The predominant intermolecular force in CaBr₂ is __________.

ionic bonding

Crystalline solids differ from amorphous solids in that crystalline solids have __________.

a long-range repeating pattern of atoms, molecules, or ions

The unit cell with all sides the same length and that has lattice points only at the corners is called __________.

primitive cubic

As a solid element melts, the atoms become __________ and they have __________ attraction for one another.

more seperated, less

Crystalline solids __________.

have highly ordered structures

covalent network or ionic

high melting point and poor eletricty conductivity

molecular or metallic

softness and relatively low melting point

metallic only

high mobility of electrons throughout the solid

covalent network only

network of covalent bonds

ionic only

charged particles throughout the solid

Which type of lattice contains a lattice point completely within the unit cell?

Body-centered cubic lattice

Which of the following solids are held together by the weakest interactions?

molecular solids

You are given a white substance that melts at 235.3 ∘C∘C; the solid is a not a conductor of electricity and is soluble in water. Which type of solid (molecular, metallic, covalent-network, or ionic) might this substance be?

molecular solid

What is a monomer?

A monomer is a small molecule with low molecular mass that can be joined together to form a polymer.