The crystal structure of lithium sulfide (Li2S) is pictured here. The length of the unit cell is 5.88 x 10^2. For this structure, determine:
a)the coordination number of Li and S
b) the number of formula nunits in the unit cell
c) the density of Li2S
there is a picture on google images... if you type in "crystal structure of lithium sulfide"......
To determine the answers to the questions, we need to understand the crystal structure of lithium sulfide (Li2S) and make some calculations.
a) The coordination number of Li and S:
The coordination number is the number of nearest neighbors or atoms that surround a central atom in a crystal structure. In the case of Li2S, each lithium (Li) atom is surrounded by 6 sulfur (S) atoms and each sulfur atom is surrounded by 3 lithium atoms.
b) The number of formula units in the unit cell:
To determine the number of formula units in the unit cell, we need to know the composition of the unit cell. In this case, the formula is Li2S, which means there are 2 lithium atoms and 1 sulfur atom in each formula unit. Since each Li atom is shared by another unit cell, we only need to consider half of the Li atoms in the unit cell. Therefore, the total number of formula units in the unit cell can be calculated by:
Number of formula units = (Number of Li atoms / 2) + Number of S atoms
Since there are 2 Li atoms and 1 S atom in each formula unit:
Number of formula units = (2 / 2) + 1 = 2
So there are 2 formula units in the unit cell.
c) The density of Li2S:
To calculate the density of Li2S, we need to know the molar mass of Li2S and the volume of the unit cell. The molar mass of Li2S can be calculated by adding the atomic masses of lithium and sulfur:
Molar mass of Li2S = (2 × atomic mass of Li) + atomic mass of S
The atomic masses of lithium and sulfur can be found on the periodic table. Next, we need to calculate the volume of the unit cell. Given that the length of the unit cell is 5.88 x 10^2, the volume of the unit cell can be calculated using the formula:
Volume of the unit cell = (Length of the unit cell)^3
Once we have the molar mass and volume, we can calculate the density using the formula:
Density = (Molar mass of Li2S) / (Volume of the unit cell)
By plugging in the calculated values, you can determine the density of Li2S.