Theoretical Density Calculator:
Enter the values of number of atoms or molecules per unit cell, n, atomic or molecular mass, A(kg/mol) and unit cell volume, V(m3) to determine the value of theoretical density, ρ(kg/m3).
Theoretical Density Formula:
Theoretical density signifies the mass per unit volume of a substance, assuming perfect packing and no defects, typically measured in kilograms per cubic metre. It reflects the intrinsic density of a material based on its atomic or molecular structure.
Higher atomic or molecular mass translates to higher theoretical density for the same volume.
The atomic or molecular arrangement in a material influences the density. Closer packing leads to higher theoretical density.
More atoms or molecules in a given volume indicate a higher theoretical density, representing the material’s compactness.
The structure acts like a blueprint for the density. More efficient packing results in higher theoretical density.
Number of atoms per unit cell – the number of atoms in the repeating unit of the crystal structure.
Atomic mass of the element – the mass of a single atom of the element.
Volume of the unit cell – the volume occupied by the repeating unit in the crystal structure.
Avogadro’s number – a constant representing an incredibly large number of atoms.
Theoretical density assumes perfect packing of atoms within the unit cell. In reality, materials may have imperfections or empty spaces, leading to a practical density lower than the theoretical value.
The number of atoms per unit cell (n) and the volume of the unit cell (V) depend on the specific crystal structure of the material. Different crystal structures can lead to different theoretical densities for the same element.
The theoretical density, ρ(kg/m3) in kilograms per cubic metres is equal to the number of atoms or molecules per unit cell, n multiplied by the atomic or molecular mass, A(kg/mol) in kilograms per mole divided by the product of the unit cell volume, V(m3) in cubic metres and Avogadro’s number, N(mol-1).
Theoretical density, ρ(kg/m3) = n * A(kg/mol) / V(m3) * N(mol-1)
ρ(kg/m3) = theoretical density in kilograms per cubic metres, kg/m3.
n = molecules per unit cell.
A(kg/mol) = atomic or molecular mass in kilograms per mole, kg/mol.
V(m3) = unit cell volume in cubic metres, m3.
N(mol-1) = Avogadro’s number, mol-1 (6.022 * 1023 mol-1).
Theoretical Density Calculation:
- Find theoretical density:
Given: n = 4, A(kg/mol) = 0.0635kg/mol, V(m3) = 1.6 * 10-29 m3, N(mol-1) = 6.022 * 1023 mol-1.
Theoretical density, ρ(kg/m3) = n * A(kg/mol) / V(m3) * N(mol-1)
ρ(kg/m3) = 4 * 0.0635 / 1.6 * 10-29 * 6.022 * 1023
ρ(kg/m3) = 0.254 / 9.6352 * 10-6
ρ(kg/m3) = 2.63 * 104kg/m3.
- Find atomic or molecular mass:
Given: n = 2, ρ(kg/m3) = 8.96 * 103kg/m3, V(m3) = 1.08 * 10-28 m3, N(mol-1) = 6.022 * 1023 mol-1.
Theoretical density, ρ(kg/m3) = n * A(kg/mol) / V(m3) * N(mol-1)
A(kg/mol) = ρ(kg/m3) * V(m3) * N(mol-1) / n
A(kg/mol) = 8.96 * 103 * 1.08 * 10-28 * 6.022 * 1023 / 2
A(kg/mol) = 5.84 * 10-2 / 2
A(kg/mol) = 0.0292kg/mol.