CHEM

Info:

The atoms of crystalline solid pack together into a three-dimensional array of many small repeating units called unit cells. The simplest of the unit cells are those that have cubic symmetry, with atoms positioned at the corners of a cube. Atoms can also be found in the sides (faces) of the cube, or centered within the body of the cube. It is important to realize that a unit cell is surrounded by other unit cells in every direction. Therefore, face and corner atoms are shared with neighboring unit cells. The fraction varies with the type of atom as shown in the following table.

Type of atom / Fraction in unit cell
corner 1/8
face 1/2
body 1

The size of a unit cell in any given solid can be calculated by using its density. This and the reverse calculation are common test questions in general chemistry courses.

**I am having problems with the following 2 questions:

1. Gallium crystallizes in a primitive cubic unit cell. The length of an edge of this cube is 362pm. What is the radius of a gallium atom?

Express your answer numerically in picometers.

"radius = _____pm"

&

2. The face-centered gold crystal has an edge length of 407pm. Based on the unit cell, calculate the density of gold.

Express your answer numerically in grams per cubic centimeter.

density = ______g/cm^3

  1. 👍
  2. 👎
  3. 👁
  1. For a primitive unit cell, a = 2r where a is the length of the edge of the cell and r is the radius.

    For the fcc gold atom, density = mass/volume.
    volume calculation:
    Volume = (edge)3. Don't forget to change the pm to cm if you want density in g/cc.

    mass calculation:
    There are 4 atoms per unit cell along the face of one cube.
    mass = (4atoms)(atomic mass Au)/6.02 x 10^23 atoms mol-1

    Then density = mass/volume

    1. 👍
    2. 👎

Respond to this Question

First Name

Your Response

Similar Questions

  1. chemistry

    what is the mass in grams? a) 3.011 x 10^23 atoms F b)1.50 x 10^23 atoms Mg c)4.50 x 10^12 atoms Cl d)8.42 x 10^18 atoms Br e) 25 atoms w f) 1 atom Au can you please explain a and b to me then i'll come back later and see if i did

  2. Sciences

    What is a substance that cannot be separated into simpler substances by physical or mechanical methods such as filtering, boiling, or sifting? A crystalline solid A sublimation A pure substance •• An amorphous solid Correct me

  3. science --- pls check my work!!!

    hi, pls check my work asap! 1. A ___ has a definite shape and a definite volume. (1 point) solid*** liquid gas molecule 2. Why is a gas able to flow? (1 point) Its particles have melted and can move around.Its particles have high

  4. chemistry

    You are analyzing a solid isolated from a reaction and find that its boiling point is over 1000 ∘C. You dissolve the compound in water solution and recrystallize it to produce some solid crystals that you use to determine that

  1. Geometry

    In a Hexagon net for a 3 dimensional solid how many regions would there be? My answer is 8 the 6 sides and the top and bottom

  2. Physics

    A weather balloon is floating at a constant height above Earth when it releases a pack of instruments. If the pack hits the ground with a velocity of -68.5 m/s, how far does the pack fall? a = -9.80 m/s^2 Vf = -68.5 m/s d = ?

  3. Chemistry (The Composition of an Atom)

    In 1808, John Dalton wrote his atomic theory of matter. The following is a list of points from that theory. If it is still considered true today, label it true. If it is not considered true today, label it false. 1)Atoms cannot be

  4. Chem - oxides

    When an element is burnt in excess oxygen, is the oxide formed always: 1. a crystalline solid 2. greater in mass than the element 3. soluble in water 4. white in color alright, i know that most oxides are not soluble in water

  1. General Chemistry

    PLEASE ANSWER VERY SOON I AM STUCK! Crystalline silicon has a cubic structure. The unit cell edge length is 543 pm. The density of the solid is 2.33 g/cm3. Calculate the number of Si atoms in one unit cell.

  2. chemistry help!!! please!!! DrBob222 I need you!!

    How many atoms of carbon are needed to produce 0.45 mol Al? 3C + 2Al2O3 4Al + 3CO2 A. 2.6 × 1026 atoms B. 9.7 × 1024 atoms C. 3.0 × 1022 atoms D. 2.0 × 1023 atoms I'm really very stuck with this question. please help me!!!

  3. math

    tony broke a larger array into 2x3 and 4x3 array what did the larger array look like

  4. science

    An igneous rock forms quickly. Which characteristic could the rock have? A. small sand grains B. evidence of folding C. smooth, sharp texture D. large mineral crystals (my answer) Which type of rock can be foliated? A. igneous

You can view more similar questions or ask a new question.