So, kilogram is not a convenient unit to measure such small mass. A different mass unit (atomic mass unit) is used for expressing atomic masses this is known as atomic mass unit. This unit is the ...

which has a mass of exactly 12. Relative atomic masses do not have units.

Accompanying Lesson Plan: Lesson 3.2: Finding Volume—The Water Displacement Method The chart shows that atomic size and mass for the first 20 elements in the periodic table. The size of the atoms and ...