The radius of a hydrogen atom is 0.0000000529177 of a millimeter. Express this number as an approximation.
1. 0.0000000053
2. 0.0000005
3. 0.00000006
4. 0.00000005
The given radius, 0.0000000529177 millimeters, can be rounded to 0.00000005 millimeters.
Therefore, the correct approximation is 4. 0.00000005.