The iodine monobromide molecule, IBr, has a bond length of 2.49 Angstrom and a dipole
moment of 1.21 D.
(b) Calculate the effective charges on the I and the Br atoms in IBr, in units of the electronic charge e.
The dipole moment is given by μ = qr, where q is the charge separated (in C) and r is the distance separating the charge. Since we're given the dipole moment (1.21 D) and the bond length (2.49 Angstrom), we solve for the charge q. Dipole moments are given in D units - recall that 1 D = 3.34 x 10-30 C-m. We convert the bond length into meters:
so the amount of charge separated by the difference in EN is 1.623x10-20 Coulombs. We want the answer in units of electronic charge e: