So, $$128 \times 10^{-12} m = 128 \times 10^{-12} m \times \frac{1 Å}{1\ times 10^{-10} m}$$ $$= 128 \times \frac{1}{10^2} Å= 1.28 Å$$

Therefore, the radius of a copper atom is 1.28 angstroms.