A metal crystallizes in bcc lattice with an edge length of 4 \AA. How many metal atoms can be placed in a two-dimensional open box of length 35 \AA and width 35 \AA?
Show Hint
For lattice-based packing problems, first determine the spacing between neighbouring atoms and then calculate the number of atoms that fit along each dimension.
Concept:
For a BCC lattice,
\[
4r=\sqrt{3}a
\]
where \(a\) is edge length.
Atoms arranged in a two-dimensional layer occupy approximately a square grid of side equal to the lattice parameter.
Step 1: Determine number of atoms along one side.
Given,
\[
a=4\AA
\]
Length of box
\[
=35\AA
\]
Number of atoms along one side
\[
\approx \frac{35}{4}+1
\]
\[
\approx 8.75+1
\]
\[
\approx 10
\]
Step 2: Determine total atoms in the square layer.
\[
N=10\times10
\]
\[
N=100
\]
Step 3: Final answer.
\[
\boxed{100}
\]