Exam 18: The Solid State a Particulate View

In ionic solids, one ion often occupies holes in the unit cell defined by the other ion.In a simple cubic cell, what are the types of holes that are found and the number of holes of each type?

Suppose, in a carbon steel, 14 out of every 100 octahedral holes in the fcc crystal lattice of Fe atoms are filled with carbon atoms.What is the approximate percent composition of the alloy by mass?

The face-centered cubic unit cell has _____tetrahedral holes.

A face-centered cubic unit cell contains______ octahedral holes.

Thorium adopts an fcc structure and has a density of 11.724 g/cm³.Estimate A) the radius of a Th atom, B) the unit cell edge length, C) the length of the face diagonal from opposite corners on one side), and D) the length of the body diagonal across the unit cell from opposite corners on opposite sides).Express your answers in picometers.The molar mass of Th is 232.0 g/cm³.

If tungsten (W) adopts a bcc structure with a unit cell edge length of 321 pm, what is the length of the body diagonal across the unit cell (from opposite corners on opposite faces)?

Based on the approximate wavelength of light emitted by the following materials, which one has the smallest band gap?

If the unit cell of copper (Cu) has an edge length of approximately 362 pm and the radius of a copper atom is approximately 128 pm, what is the probable crystal structure of copper?

Metalic solids are good conductors of electricity because

An allotrope of carbon displaying a sheet structure is

The thermal and electrical insulating qualities of ceramics can be explained by

Gallium arsenide GaA(s) is a semiconductor with a band gap of approximately 137 kJ/mol.The band gap of gallium nitride (GaN) is about 2.39 times greater than that of GaAs.What wavelength of light does each material emit when electrons in the conduction band fall back into the valence band? Express your answers in nanometers.

Aluminum (Al) has a density of 2.70 g/cm³ and crystallizes in a face-centered cubic structure.What is the unit cell edge length in picometers?

Iron (Fe) has a density of 7.87 g/cm³ and crystallizes in a body-centered cubic structure.What is the atomic radius of iron?

Iron exhibits polymorphism, the ability of a solid material to exist in more than one crystal form.At low to moderate temperatures, it adopts a bcc structure; at temperatures above 913 $\degree$ C, it adopts an fcc structure.Silicon carbide also has polymorphs, including the wurtzite form with abab packing and the sphalerite form with abcabc packing.Which of the following statements is NOT correct?

Sodium (Na, 22.99 g/mol) and potassium (K, 39.10 g/mol) both adopt a bcc structure.The radius of a potassium atom is approximately 1.23 times that of a sodium atom, and potassium's bulk density is about 1.98 g/cm³.What is the approximate density of sodium?

In fluorite,

Boron( r = 88 pm) is sometimes added to steel alloys as a hardening agent.Suppose one alloy contains approximately one B atom for every 1920 Fe atoms(r = 126 pm).Which of the following statements regarding the boron in alloy is correct?

Which element would be used to dope germanium (Ge) to produce an n-type semiconductor?

Molecular orbital theory can be applied