1. PARTS OF AN ATOM

2. How Small Is An Atom?
A penny has 20,000,000,000,000,000,000,000 atoms.
2 x 1022

3. An aluminum atom has a diameter of about 0. 00000003 cm
An aluminum atom has a diameter of about cm. That is three one-hundred-millionth of a centimeter.
3 x 10-8

4. The mass of a proton is about 0.0000000000000000000000017 g.
1.7 x g

5. Because the masses of subatomic particles (protons and neutrons) in atoms are so small, scientists made a new SI (metric) unit for them.
The SI unit for the masses of particles in atoms is the atomic mass unit (amu)