Chemistry: The Central Science (13th Edition)

The atomic radius of Bi is estimated to be $1.42$ angstrom.
A crude estimate of the Bi-I bond length (C) would be: $$A+B=C$$ where $A$ is the bonding atomic radius of Bi and $B$ is the bonding atomic radius of I. Since we already know the experimental Bi-I bond length and the bonding atomic radius of I, we can deduce the atomic radius of Bi by subtracting the atomic radius of I from the bond length. The experimental Bi-I bond length is $2.81$ angstrom and the atomic radius of I, from figure 7.7, is $1.39$ angstrom. Therefore, the atomic radius of Bi would be $$2.81-1.39=1.42 (angstrom)$$