Radius of a potassium atom

[Chrizac]

Potassium metal crystallizes in a body-centered cubic structure with a
unit cell edge length is 5.31A. The radius of a potassium atom is
2.30 A. WHY???

Im not sure if this is where I should put this question but I need to
know. ASAP!!! Studying for finals.

[beavith]

Post by Chrizac
Potassium metal crystallizes in a body-centered cubic structure with a
unit cell edge length is 5.31A. The radius of a potassium atom is
2.30 A. WHY???
Im not sure if this is where I should put this question but I need to
know. ASAP!!! Studying for finals.

apply pythagoras' theorem. do the math.

is that a K ion or atom?

[LOUIS]

First ask yourself what is centered cubic structure.
Then imagine the atoms of K to be spheres.
Then apply the sphere in a cubic centered structure knowing that the
cristalline cell lenght link two atomic center together.

Look at this lamellar cut of the cristall cell following one of the
orthogonal axis of the space through one side of the centered cube:

O O O O O
O O O O
O O O O O
It is logical the cristall cell is bigger than a simple juxtaposition of
two atom radii = 4,6 A°

Now apply vectorial geometry (in the 3D space) (math cursus) and you'll
get the answer.
A good tip is that the cube is fully symetric and that the first layer
display V, < , > and ... perpendicular angles between the corner
atoms.... ----> Simple pythagore not even generalised theorem with
unperpendicular angles.

Ph Z

Post by Chrizac
Potassium metal crystallizes in a body-centered cubic structure with a
unit cell edge length is 5.31A. The radius of a potassium atom is
2.30 A. WHY???
Im not sure if this is where I should put this question but I need to
know. ASAP!!! Studying for finals.