Problem: The unit cell of MgO is shown below.Does MgO have a structure like that of NaCl or ZnS? If the density of MgO is 3.58 g/cm3, estimate the radius (in centimeters) of the O2- anions and the Mg2+ cations.

🤓 Based on our data, we think this question is relevant for Professor Davis' class at UCF.

FREE Expert Solution

NaCl  face-centered cubic (FCC)  lattice 

  • contains an atom in each of the face of the cube and an atom in each of the corners


ZnS  body-centered cubic (BCC) unit cell 

  •  composed of a cube with one atom at each of its corners and one atom at the center of the cube. 


MgO:

  • Has one O2- ion:
    • at each corner
    • at each face

MgO follows an FCC cubic lattice, similar to NaCl structure.


# of atoms=8×18+6(12)

# of atoms = 4 per 1 unit cell


Step 1: Solve for volume using density:


density =massvolumevolume=massdensity


volume=4 atoms1 unit cell×1 mol MgO(6.022×1023) atoms×40.3 g MgO1 mol MgO ×1 cm33.58 g MgO


volume = 7.477 x 10-23 cm3/1 unit cell

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Problem Details

The unit cell of MgO is shown below.

Does MgO have a structure like that of NaCl or ZnS? If the density of MgO is 3.58 g/cm3, estimate the radius (in centimeters) of the O2- anions and the Mg2+ cations.

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What scientific concept do you need to know in order to solve this problem?

Our tutors have indicated that to solve this problem you will need to apply the Unit Cell concept. You can view video lessons to learn Unit Cell. Or if you need more Unit Cell practice, you can also practice Unit Cell practice problems.

What professor is this problem relevant for?

Based on our data, we think this problem is relevant for Professor Davis' class at UCF.

What textbook is this problem found in?

Our data indicates that this problem or a close variation was asked in Chemistry: An Atoms First Approach - Zumdahl 2nd Edition. You can also practice Chemistry: An Atoms First Approach - Zumdahl 2nd Edition practice problems.