Question

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

Explanation:

Atoms are extremely small. Picometers are the most appropriate SI - unit for expressing atomic radii as atoms have radii on the order of 30 - 300 pm. Millimeters, micrometers, and nanometers are too large for this purpose.

Answer:

B. 1 picometer (pm)