Lattice parameter + valence + avg time between collisions

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exzacklyright
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valence Z=1, lattice param a = 4.05 conductivity = 1.76e7 . What's the avg time between collisions of a conduction electron in this metal (bcc structure).really have no idea lol
 
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The equation I think I got to use is : [itex]\tau[/itex]=([itex]\sigma[/itex]*m)/ (n*e^2)

n= 2.52 e28 sigma = 2.38e7 and I'm guessing e = 1.6e-19 but i got the wrong answer.
 
How did you get the value for n? It seems that you have an error there.
 
Since the crystal structure of Na is bcc, there are two Na atoms in each conventional unit cell of volume a^3. Denisty n= 2/a^3... so 2/(4.3e-10)^3=2.52e28
 
In the original post you said that the lattice constant is 4.05A (and not 4.3).
Which one is it?
 
nasu said:
In the original post you said that the lattice constant is 4.05A (and not 4.3).
Which one is it?

ah sorry. in the example problem it's 4.3 but in the homework problem it's 4.05