1. Nov 20, 2009

### Dell

for the calculations in one of my homework questions, i need to use the atomic radii of Fe and Ni, the problem is that every site i come accross gives me different values

Fe
wikipedia 126pm
chemicool 140pm

how do i know which one to "trust" ?

2. Nov 20, 2009

### chemisttree

Is that zero valent iron and nickel or one of their ions?

The ionic radii for ions are a function of their coordination number and oxidation #.

3. Nov 21, 2009

### Staff: Mentor

I think I have seen such data on IUPAC site, even if it is not correct, source sounds as reliably as possible.

No idea what is the definition of atomic radius, could be differences can be attributed to different understanding of what the atomic radius is.

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4. Nov 21, 2009

### chemisttree

It is likely the atomic radius in gas phase. Putting a metal atom in a metal lattice can change the radius as well.

5. Nov 21, 2009

### Staff: Mentor

That's more or less what I am aiming at - depending on the way you want it, you will get different numbers. Even in the gas phase it is not obvious to me what 'size' means, as atoms don't end abruptly

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6. Nov 22, 2009

### Dell

im really confused,, the question goes like this

find the plane density for the plane [1 1 1] of the following:

iron (BCC)
nickel (FCC)

for [111] i know that
BCC- R=sqrt(3)/4*a
FCC- R=sqrt(2)/4*a

PD=n/A

BCC[111]- PD=sqrt(3)/(16*R^2)
FCC[111]- PD=sqrt(3)/(6*R^2)

now all i need to do is find the CORRECT radius to use, i used
FE 126pm
Ni 124 pm

and got

PD(Fe)= 6.818*10^-6 [atoms/pm^2]
PD(Ni)= 1.877*10^-5 [atoms/pm^2]

but i dont know if thats right

7. Nov 23, 2009

### chemisttree

Last edited by a moderator: Apr 24, 2017