<u>Answer</u>:
"The arrangement of atoms or ions in a crystal " is described by the terms body-centered cubic and face-centered cubic.
<u>Explanation</u>:
Face centred cubic system explains the crystal structure where an atom is present at each cubic corner of the crystal and the centre of each cube face. Meaningfully, a closed packed plane where at each "face of the cube" atoms touch the alongside face diagonals.
Whereas in body centric cube system has the lattice point present at the 8 corners of cell and an additional one at the center of the cell. Thus, both explains how the atom or ions are placed or arranged in a crystal.
Moles of ammonium sulfate = 26.42/molar mass of (NH4)2SO4
= 26.42/132.14 = 0.19 mole.
Molarity = moles of ammonium sulfate/volume of solution
= 0.19/50x10^-3
= 3.8M
Compare them accordingly with the formula of E=hc/wavelength
