Which of the following units are used frequently for atomic radii ?

Options

A. meter
B. picometers
C. kilometers
D. centimeters

Answer

To determine the units frequently used for atomic radii, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding Atomic Size**:
- Atomic radii refer to the size of an atom, which is extremely small. Therefore, we need to use a unit that can accurately represent such small dimensions.

2. **Common Units for Measurement**:
- The most common units used for measuring atomic radii are picometers (pm).
- Other units like nanometers (nm) and angstroms (Å) are also used but are less frequent compared to picometers.

3. **Conversion of Units**:
- To understand the scale, it's important to know that:
- 1 picometer = \(10^{-12}\) meters
- 1 nanometer = \(10^{-9}\) meters
- 1 angstrom = \(10^{-10}\) meters
- Given that atomic radii are on the order of picometers, this unit is preferred.

4. **Example of Atomic Radius**:
- For instance, the atomic radius of hydrogen is approximately 37 picometers. This illustrates how small atomic dimensions are, reinforcing the use of picometers as a standard unit.

5. **Conclusion**:
- Therefore, the unit frequently used for atomic radii is picometers (pm).

### Final Answer:
The unit frequently used for atomic radii is **picometers (pm)**.

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