Which SI unit is commonly used to measure the size (radius or diameter) of atoms?

• A. kilogram (kg)
• B. liter (L)
• C. nanometer (nm)
• D. ampere (A)

Answer: (C)

Verified step by step guidance

1. Understand that the size of atoms is extremely small, typically on the order of picometers to nanometers.
2. Recall that the SI base units like kilogram (kg) measure mass, liter (L) measures volume, and ampere (A) measures electric current, so these are not appropriate for measuring atomic size.
3. Recognize that the nanometer (nm) is a unit of length equal to 10^{-9} meters, which is suitable for expressing atomic dimensions.
4. Conclude that the nanometer (nm) is the commonly used SI unit to measure the size (radius or diameter) of atoms.
5. Therefore, when measuring atomic sizes, always use units of length such as nanometers rather than units of mass, volume, or electric current.