Question

which si unit of length is most commonly used to indicate the radius of an atom?
a 1 micrometer (μm)
b 1 nanometer (nm)
c 1 picometer (pm)
d 1 millimeter (mm)

Explanation:

Atoms are extremely small. Picometers are the most appropriate SI - unit for measuring atomic radii as atoms have radii in the range of a few tenths to a few hundred picometers. Micrometers, nanometers, and millimeters are too large for this purpose.

Answer:

C. 1 picometer (pm)