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Lithium crystallizes in a bcc structure with an edge length of 3.509 Å.
Calculate its density. What is the approximate metallic radius of lithium in picometers?
(atomic weight of Li = 6.94)
Given: Edge length, a=3.509 = 3.509*10-8 cm
Atomic weight (Molecular weight) of Lithium, M=6.94 g/mol
In a BCC structure, number of atoms per unit cell, n=2 atoms
Mass of lithium, m is
where NA is Avogadro's Number, NA= 6.022*1023 atoms/mol
Volume of a BCC cell is V=a3
V=(3.509*10-8 cm)3
V=4.320*10-23 cm3
Thus the density of Lithium is
The edge length of a BCC crystal structure is
where r is the Atomic Radius or Metallic Radius
Thus, the density of Lithium is 0.533 g/cm3 and metallic radius is 151.9 pm