[mickfortis]

I'm currently doing a chemistry lab report about Avogadro's Number and am having trouble answering 2 questions...
The first one is "Find the side length of the Unit Cell of the crystalline structure of Iron and Aluminium3
The second: "Find the number of atoms present in one unit cell of each of the crystalline structures"
Ive searched on the internet but havent found anything
your help is appreciated

[mickfortis]

Somebody please answer.... I need to know the answers to these questions.

[mickfortis]

Some helpful people here huh....

[sjb]

Some helpful people here huh....

Bear in mind it's a Sunday, for one.

If you're doing this in terms of Avogadro's number, there may be a more useful way around this, but does http://www.google.co.uk/search?q=iron+crystal+structure help?

[Borek]

Start with the density, calculate volume of a single cell (that's where Avogadro's number comes in handy), assume it is just a cube and calculate length of the edge. Not exact but better than nothing.

[mickfortis]

Some helpful people here huh....

Bear in mind it's a Sunday, for one.

If you're doing this in terms of Avogadro's number, there may be a more useful way around this, but does http://www.google.co.uk/search?q=iron+crystal+structure help?

Thanks for your help man! Much appreciated.
I assume the "cell parameters" (a,b,c) in the first link of that google search correspond to the side length i am looking for?

[Suella]

To solve this problem with density and the nature of the element as givens, you need to know the number of atoms contained in a unit cell. Fe has a bcc structure, therefore there are two Fe atoms per unit cell. Al, on the other hand, has a ccp structure and therefore a unit cell of Al has four atoms. Now you can use the molar masses, density, avogadro's number to find the volume of the unit cell, and root 3 will give you the edge-length of the cube. Therefore proceed as follows

Volume of unit cell= g/cm³ x mol/g x Avogadros number of atoms/mol x unit cell volume/number of atoms in unit cell

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